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8/6/2019 hp_ContAccess_xp1024UG Rootsan technologies Pvt Ltd

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HP StorageWorks

Continuous Access XP user guidefor the XP1024/XP128

Part number: T1611-96002Second edition: March 2006


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Legal and notice information

Copyright 2005, 2006 Hewlett-Packard Development Company, L.P.

Confidential computer software. Valid license from HP required for possession, use or copying. Consistent with FAR 12.211 and 12.212,Commercial Computer Software, Computer Software Documentation, and Technical Data for Commercial Items are licensed to the U.S. Governmentunder vendors standard commercial license.

The information contained herein is subject to change without notice. The only warranties for HP products and services are set forth in the expresswarranty statements accompanying such products and services. Nothing herein should be construed as constituting an additional warranty. HP shallnot be liable for technical or editorial errors or omissions contained herein.

Adobe and Acrobat are trademarks of Adobe Systems Incorporated.

Hitachi Data Systems is a registered trademark and service mark of Hitachi, Ltd., and the Hitachi Data Systems design mark is a trademark andservice mark of Hitachi, Ltd.

Hitachi Freedom Storage, Hitachi Graph-Track, Hitachi TrueCopy, and Lightning 9900 are trademarks of Hitachi Data Systems Corporation.

UltraNet Storage Director is a registered trademark or trademark of Computer Network Technology Corporation (CNT).

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AIX, ESCON, IBM, and S/390 are registered trademarks or trademarks of International Business Machines Corporation.

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UNIX is a registered trademark of The Open Group in the United States and other countries.

All other brand or product names are or may be trademarks or service marks of and are used to identify products or services of their respectiveowners.

Continuous Access XP user guide for the XP1024/XP128


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Continuous Access XP user guide for the XP1024/XP128 3

About this guide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Intended audience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Prerequisites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Firmware versions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Related documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Document conventions and symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10HP technical support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Subscription service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Helpful web sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1 Continuous Access XP for the XP1024/XP128 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Overview of Continuous Access XP operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14XP1024/XP128 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Main and remote control units (MCUs and RCUs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Volume pairs (P-VOLs and S-VOLs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Continuous Access XP Asynchronous consistency groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Remote copy connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Initiator ports and RCU target ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Remote control ports (RCPs) and local control ports (LCPs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Command View XP management station or XP Remote Web Console . . . . . . . . . . . . . . . . . . . . . . 18Host failover software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Remote copy operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Initial copy operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Update copy operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Read and write I/O operations for Continuous Access XP volumes . . . . . . . . . . . . . . . . . . . . . . . . 20S-VOL write option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Continuous Access XP Asynchronous recordset operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Creating and storing recordsets at the MCU. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Sending recordsets to the RCU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Storing recordsets at the RCU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Selecting and settling recordsets at the RCU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Types of recordsets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Inflow control of recordsets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Inflow control by MCU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Inflow control by RCU. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Continuous Access XP Asynchronous consistency group operations . . . . . . . . . . . . . . . . . . . . . . . . . . 23Group options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Copy pending timeout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24RCU ready timeout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Group operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Continuous Access XP volume pair status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Continuous Access XP LUSE pair status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Continuous Access XP Asynchronous pair status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Continuous Access XP split types (PSUS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Continuous Access XP suspend types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Continuous Access XP Asynchronous suspension conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Preparing for Continuous Access XP operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30System requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Requirements and restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

One-to-one volume copy operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Logical unit (LU) types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Consistency groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Accessing Continuous Access XP P-VOLs and S-VOLs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Contents


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Cache and nonvolatile storage (NVS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Host failover software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Duplicate volumes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Host system crash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Installing hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Fibre Channel remote copy connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Serial remote copy connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Configuring MCUs and RCUs for Continuous Access XP operations . . . . . . . . . . . . . . . . . . . . . . . . . . 37Fibre Channel and serial interface configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Combining Continuous Access XP with other data management operations . . . . . . . . . . . . . . . . . . . . 39Combining Continuous Access XP and BC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Starting Continuous Access XP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Continuous Access XP panes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42Continuous Access XP main pane (Pair Operation pane) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Volume list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44Display Filter pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45Continuous Access XP Snapshot function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46Creating and exporting (downloading) Continuous Access XP snapshot files . . . . . . . . . . . . . . . . . 47

RCU Operation pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47CU Number tree and MCU/RCU list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48Port tree and Port list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Asynchronous Operation pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49Usage Monitor pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51History Operations pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Performing Continuous Access XP configuration operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53MCU operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Configuring MCU ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54RCU operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Viewing RCU Status (RCU Status) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55Registering RCUs (Add RCU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Registering RCUs to the connected MCU. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59Modifying RCU options (Change RCU Option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60Deleting RCUs (Delete RCU). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61RCU path parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Adding and deleting logical paths for RCUs (Add Path/Delete Path) . . . . . . . . . . . . . . . . . . . . . . . 62Adding new logical paths from the connected MCU to an existing RCU:. . . . . . . . . . . . . . . . . . 63Deleting paths from the connected MCU to an existing RCU:. . . . . . . . . . . . . . . . . . . . . . . . . . 63

Adding and deleting SSIDs for RCUs (Add SSID/Delete SSID) . . . . . . . . . . . . . . . . . . . . . . . . . . . 64Port change operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65Modifying parameters and deleting settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

Modifying parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66Deleting RCUs, paths, or SSIDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

Continuous Access XP Asynchronous operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66Viewing consistency group status (CT Group Status) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67Adding consistency groups (Add CT Group) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68Modifying consistency group options (CT Group Option). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

Deleting consistency groups (Delete CT Group). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70Asynchronous copy option. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70Modifying parameters and deleting consistency groups. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Modifying parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72Deleting consistency groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Usage Monitor operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73Starting and stopping monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Starting remote copy usage monitoring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73Stopping remote copy usage monitoring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Displaying usage monitor graph. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73Optimizing Continuous Access XP operations and disk array performance . . . . . . . . . . . . . . . . . . . . . 76Discontinuing Continuous Access XP operations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Performing Continuous Access XP pair operations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78


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Preparing for Continuous Access XP volume pair operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78Common procedure for Continuous Access XP pair operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

List after command selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79Modifying parameters and deleting LUs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

Modifying LU parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79Deleting LUs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

Viewing Continuous Access XP pair status for LUs and LDEVs (Pairdisplay) . . . . . . . . . . . . . . . . . . . . . 80Creating Continuous Access XP volume pairs (Paircreate) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

Continuous Access XP initial copy and pair options of the Paircreate pane. . . . . . . . . . . . . . . . . . . 84

Fence Level (Continuous Access XP Synchronous only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84Initial Copy parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84Asynchronous parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

Splitting Continuous Access XP pairs (Pairsplit-r). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85Resuming Continuous Access XP volume pairs (Pairresync) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88Deleting Continuous Access XP volume pairs (Pairsplit-S). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90Changing pair options (Change Pair Option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93Using Continuous Access XP for data migration and duplication . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

Data migration using Continuous Access XP Synchronous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94Point-in-Time data duplication using Continuous Access XP Asynchronous . . . . . . . . . . . . . . . . . . . 95

Powering off and on Continuous Access XP components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95Planned outage of MCUs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

Planned outage of RCUs or remote copy connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96Planned outage of MCUs and RCUs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96Continuous Access XP disaster recovery operations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Preparing for disaster recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97Considering the P-VOL fence-level setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97Setting the fence level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98Transferring sense information between sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99File and database recovery procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Switching operations to remote sites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100Analyzing currency of Continuous Access XP Synchronous S-VOLs . . . . . . . . . . . . . . . . . . . . . . . 100Analyzing consistency of Continuous Access XP Asynchronous S-VOLs . . . . . . . . . . . . . . . . . . . . 101

Transferring operations back to primary sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102Resuming normal operations at primary sites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

Error codes and messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103Continuous Access XP error codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103Service Information Messages (SIMs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

Pinned track recovery for Continuous Access XP volumes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

Figures1 Continuous Access XP components for Fibre Channel connections . . . . . . . . . . . . . . . . . . . . . . . . . . 142 Continuous Access XP components for Serial (ESCON) connections . . . . . . . . . . . . . . . . . . . . . . . . . 153 Remote copy operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 Selecting and settling Continuous Access XP Async recordsets at the RCU. . . . . . . . . . . . . . . . . . . . . 225 Fibre Channel remote copy connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346 Direct connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347 Switch connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 358 Extender connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359 Serial remote copy connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3510 N pairs of remote copy connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3611 N-to-1 and 1-to-n remote copy connections (n less than or equal to 4). . . . . . . . . . . . . . . . . . . . . . . . 3612 Remote copy connections shared with channel-to-RCU connections. . . . . . . . . . . . . . . . . . . . . . . . . . 3713 Add RCU and RCU Option panes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3814 Async Option and Add CT Group panes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3815 Shared Continuous Access XP P-VOL and shared BC P-VOL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4016 Shared Continuous Access XP S-VOL and shared BC P-VOL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4017 Shared Continuous Access XP/BC P-VOL and shared Continuous Access XP S-VOL/BC P-VOL . . . . . . 41


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18 Shared BC S-VOL/Continuous Access XP P-VOL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4119 Continuous Access XP main pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4220 Volume list (partial view). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4421 Display Filter pane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4622 RCU Operation pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4823 RCU Operation pane with the MCU&RCU option button selected . . . . . . . . . . . . . . . . . . . . . . . . . . 4824 RCU Operation pane with the Port option button selected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4925 Asynchronous Operation pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5026 Usage Monitor pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

27 History Operations pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5228 RCU Status pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5529 Add RCU pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5730 RCU Option pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5831 RCU Settings Parameter list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5932 RCU Option pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6033 RCU Settings Parameter list (RCU Option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6034 Fibre Channel interface connections going through switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6135 Add RCU pane used for configuration in Figure 34 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6236 Add Path pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6237 Add SSID pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6438 Changing port types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

39 CT Group Status pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6740 Add CT Group pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6841 CT Group Option pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6942 Consistency Group Settings Parameter list. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7043 Async Option pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7144 Asynchronous Option Settings Parameter list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7245 Display Item pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7446 Pairdisplay pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8047 Paircreate pane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8148 Pair Settings Parameter list (Paircreate) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8349 Pairsplit-r pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8650 Pair Settings Parameter list (Pairsplit-r) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8851 Pairresync pane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

52 Pair Settings Parameter list (Pairresync). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9053 Pairsplit-S pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9154 Pair Settings Parameter list (Pairsplit-S) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9355 Change Pair Option pane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9356 Pair Settings Parameter list (Pair Option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9457 Relationship between log file and data file in PAIR status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Tables1 Recommended and minimum firmware versions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 Document conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 Continuous Access XP supported RAID level configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 Sidefile threshold values for Continuous Access XP Asynchronous operations and write pending operations

235 Continuous Access XP Asynchronous pair status descriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 Continuous Access XP split types (PSUS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 Consistency status descriptions for split/suspended Continuous Access XP Async S-VOLs . . . . . . . . . . . 288 Continuous Access XP suspend types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 Continuous Access XP Asynchronous suspension conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3010 Host pair status reporting for Continuous Access XP, BC, and Continuous Access XP/BC shared volumes4011 Data currency of a shared Continuous Access XP/BC volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4012 Continuous Access XP functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4213 Volume icons for Continuous Access XP operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4414 Status icons for Continuous Access XP operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4515 Snapshot functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4716 Logical path status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56


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About this guideThis guide provides information about the following:

Overview of Continuous Access XP operations on page 13

Preparing for Continuous Access XP operations on page 30

Starting Continuous Access XP on page 41

Performing Continuous Access XP configuration operations on page 53 Performing Continuous Access XP pair operations on page 78

Continuous Access XP disaster recovery operations on page 97

Error codes and messages on page 103

Pinned track recovery for Continuous Access XP volumes on page 103

Intended audienceThis guide is intended for customers and HP-authorized service providers with knowledge of the following:

Disk array hardware and software

Data processing and RAID storage subsystems and their basic functions

NOTE: The functions described in this manual may be limited, depending on your assigned level of useraccess. Some users will have read-only access while others will have limited or full array access. Foradditional information on users and user groups, please see the HP StorageWorks XP Remote WebConsole user guide.

PrerequisitesPrerequisites for using this product include:

Installation of the HP StorageWorks disk array(s)

Installation of the license key for this product

Firmware versionsThe recommended firmware versions shown in Table 1 provide the optimal level of support for thefeatures provided with this product. Older firmware versions can be used; however, product featuresenabled with newer firmware will not appear.

Related documentationIn addition to this guide, please refer to other documents for this product: HP StorageWorks XP Remote Web Console user guide for XP1024/XP128

HP StorageWorks External Storage XP user guide

HP StorageWorks XP Disk/Cache Partition user guide

You can find these documents at http://www.hp.com/support/rwc/manuals

Table 1 Recommended and minimum firmware versions

XP disk array Minimum Recommended

XP1024/XP128 21-14-14-00/00 or later 21-14-18-00/00 or later
http://www.hp.com/support/rwc/manuals/http://www.hp.com/support/rwc/manuals/


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10

Document conventions and symbols

CAUTION: Indicates that failure to follow directions could result in damage to equipment or data.

IMPORTANT: Provides clarifying information or specific instructions.

NOTE: Provides additional information.

TIP: Provides helpful hints and shortcuts.

HP technical supportTelephone numbers for worldwide technical support are listed on the HP support web site:http://www.hp.com/support/.

Collect the following information before calling:

Technical support registration number (if applicable)

Product serial numbers Product model names and numbers

Applicable error messages

Operating system type and revision level

Detailed, specific questions

For continuous quality improvement, calls may be recorded or monitored.

Subscription serviceHP strongly recommends that customers register online using the Subscribers choice web site athttp://www.hp.com/go/e-updates.

Table 2 Document conventions

Convention Element

Blue text: Table 1 Cross-reference links and e-mail addresses

Blue, underlined text: (http://www.hp.com) Web site addresses

Bold text Keys that are pressed

Text typed into a GUI element, such as a box

GUI elements that are clicked or selected, such asmenu and list items, buttons, and check boxes

Italic text Text emphasis

Monospace text File and directory names

System output

Code

Commands, their arguments, and argument values

Monospace, italic text Code variables

Command variables

Monospace, bold text Emphasized monospace text
http://www.hp.com/support/http://www.hp.com/go/e-updates/http://www.hp.com/go/e-updates/http://www.hp.com/support/


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Subscribing to this service provides you with e-mail updates on the latest product enhancements, newestdriver versions, and firmware documentation updates as well as instant access to numerous other productresources.

After subscribing, locate your products by selecting Business support and then Storage under ProductCategory.

Helpful web sitesFor additional information, see the following HP web sites:

http://www.hp.com http://www.hp.com/go/storage

http://www.docs.hp.com

http://www.hp.com/support/rwc/manuals
http://www.hp.com/http://www.hp.com/go/storage/http://www.docs.hp.com/http://www.hp.com/support/rwc/manuals/http://www.hp.com/go/storage/http://www.hp.com/http://www.hp.com/support/rwc/manuals/http://www.docs.hp.com/


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1 Continuous Access XP for the XP1024/XP128HP StorageWorks Continuous Access XP creates and maintains duplicate copies of user data from a localdisk array on a remote disk array. These copies are useful for data duplication, backup, and disasterrecovery. Continuous Access XP has synchronous and asynchronous copy modes to accommodate a widevariety of user requirements and data copy or movement scenarios. Continuous Access XP is used foropen systems data.

If a system failure or disaster occurs at the primary (main) site, Continuous Access XP simplifies andexpedites disaster recovery procedures.

Continuous Access XP operations are nondisruptive and allow the primary (main) volume of eachContinuous Access XP volume pair to remain online to all hosts for read and write I/O operations. Afteroperations are established, Continuous Access XP operations continue unattended to provide continuous,real-time data backup. Continuous Access XP operations can be performed across distances of up to 500meters with a direct connection, 10 km (6.6 miles) using single-mode longwave optical fibre cables in aswitch configuration, 30 km (18.6 miles) using single-mode fiber with long-haul lasers in a switchedconnection, and up to 100 km using DWDM in a switched configuration. For serial interface connection,Continuous Access XP operations can be performed across distances of up to 43 km (26.7 miles) usingstandard ESCON support. Long-distance solutions are provided, based on user requirements andworkload characteristics, using approved channel extenders and communication lines.

Continuous Access XP operations can be performed with Business Copy XP operations (see Overview ofContinuous Access XP operations on page 13) to provide multiple internal copies of Continuous AccessXP volumes. Continuous Access XP also supports LU Size Expansion (LUSE), Custom Volume Size (CVS),and HP Cache LUN volumes. See Combining Continuous Access XP with other data managementoperations on page 39 for more information.

Overview of Continuous Access XP operationsContinuous Access XP provides a storage-based hardware solution for disaster recovery, which enablesfast and accurate system recovery. After Continuous Access XP operations are established, duplicatecopies of data are automatically maintained for backup and disaster recovery purposes. During normalContinuous Access XP operations, primary volumes remain online to all hosts and continue processing

read and write I/O operations. If a disaster or system failure occurs, the secondary copy of data can berapidly invoked to allow recovery with a very high level of data integrity. Continuous Access XP can alsobe used for data duplication and migration tasks.

Continuous Access XP Synchronous provides volume-based real-time data replication and is ideal forhigh-priority data backup, duplication, and migration tasks. If a disaster or system failure occurs at theprimary site, secondary Continuous Access XP Synchronous data can be rapidly invoked to allowrecovery at the volume level with an extremely high level of data integrity and currency. Up to a distanceof approximately 7-9 km, Continuous Access XP Synchronous provides the highest theoretical throughput.

Continuous Access XP Asynchronous represents a unique and outstanding disaster recovery solution forlarge amounts of data spanning multiple volumes. The Continuous Access XP Asynchronous group-basedupdate sequence consistency solution enables fast and accurate database recovery after a disaster,

without time-consuming data recovery procedures. Continuous Access XP Asynchronous (ContinuousAccess XP Async) volume groups at the remote site can be recovered with full update sequenceconsistency, but data currency might be behind the primary site due to the asynchronous remote copyoperations.

Continuous Access XP Asynchronous provides update sequence consistency for user-defined groups ofvolumes (such as large databases) and protection for write-dependent applications if a disaster occurs.Beyond a distance of 7-9 km, Continuous Access XP Asynchronous provides the highest possibletheoretical throughput.

This overview of Continuous Access XP operations describes:

Components on page 14

Remote copy operations on page 19


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14 Continuous Access XP for the XP1024/XP128

Continuous Access XP Asynchronous recordset operations on page 21

Continuous Access XP Asynchronous consistency group operations on page 23

Continuous Access XP volume pair status on page 25

ComponentsContinuous Access XP operations involve the XP1024/XP128 at a primary and secondary (remote) site,physical communications paths between these disk arrays, and Command View XP or XP Remote WebConsole. Continuous Access XP copies online data at the primary site to volumes at the secondary site via

dedicated Fibre Channel and/or ESCON remote copy connections.Host failover software is required for effective disaster recovery with Continuous Access XP.

Figure 1 and Figure 2 show Continuous Access XP components and the following functions:

XP1024/XP128 on page 15

Main and remote control units (MCUs and RCUs) on page 15

Volume pairs (P-VOLs and S-VOLs) on page 16

Continuous Access XP Asynchronous consistency groups on page 16

Remote copy connections on page 17

Initiator ports and RCU target ports on page 17

Remote control ports (RCPs) and local control ports (LCPs) on page 18

Command View XP management station or XP Remote Web Console on page 18

Host failover software on page 18

Figure 1 Continuous Access XP components for Fibre Channel connections


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Figure 2 Continuous Access XP components for Serial (ESCON) connections

XP1024/XP128

Continuous Access XP operations involve primary (main) disk arrays and secondary (remote) disk arrays(MCUs and RCUs). This document describes Continuous Access XP operations in which the main diskarray is an XP1024/XP128 and the remote disk array is an XP1024/XP128. MCUs contain ContinuousAccess XP primary volumes (P-VOLs), which contain original data and are online to the hosts. RCUscontain Continuous Access XP secondary volumes (S-VOLs), which are synchronous or asynchronouscopies of the P-VOLs. Continuous Access XP supports all CU images and logical volumes of the disk arrayand all physical hard drive options. Continuous Access XP supports RAID1 and RAID5 configurations forthe XP1024/XP128.

To provide greater flexibility and enable the disk array to be tailored to unique customer operatingrequirements, additional operational parameters, or optional modes, are available for the disk array. Atinstallation, modes are set to their default values, so discuss these settings with your HP support team.Modes can only be changed by your HP support team representative.

Contact your HP account support representative for the latest mode information.

Main and remote control units (MCUs and RCUs)

The main control unit (MCU) and remote control unit (RCU) control Continuous Access XP operations:

The MCU is the control unit in the primary disk array that controls the P-VOLs of the Continuous AccessXP volume pairs. For Command View XP, the management station must be LAN-attached to the MCUof each Continuous Access XP pair. For XP Remote Web Console and Command View XP, you need

connectivity between the arrays managed in the environment and the Web clients used to managethem. The MCU communicates with the RCU via dedicated Fibre Channel remote copy connections.The MCU controls host I/O operations to the Continuous Access XP P-VOLs and Continuous Access XPinitial copy and remote copy operations between the P-VOLs and S-VOLs. The MCU also managesContinuous Access XP pair status and configuration information.

The RCU is the CU in the remote disk array that controls the S-VOLs of the Continuous Access XPvolume pairs. The RCU assists in managing Continuous Access XP pair status and configuration (forexample, rejects write I/Os to Continuous Access XP S-VOLs). The RCU executes remote copyoperations issued by the MCU. For Command View XP, the management station must beLAN-attached to the RCU of each Continuous Access XP pair. For XP Remote Web Console andCommand View XP, you need connectivity between the arrays managed in the environment and theWeb clients used to manage them. The RCUs should also be attached to a host system to allow sense


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information to be reported if a problem with a secondary volume or remote disk array occurs andprovide disaster recovery capabilities.

The MCU and RCU can be defined separately for each Continuous Access XP volume pair. TheXP1024/XP128 CU can function simultaneously as an MCU for one or more P-VOLs and as an RCU forone or more S-VOLs, provided the remote copy connections and Fibre Channel or serial interface portsare properly configured. The XP1024/XP128 provides up to 32 logical CU images (0-1F), with each CUimage controlling up to 256 logical devices (LDEVs). Use Continuous Access XP to select the CU image inthe connected MCU and specify the CU image in the RCU. Continuous Access XP operations can beperformed on all LDEVs except the XP1024/XP128 command device.

NOTE: When serial interface connections are used for remote copy operations, controller emulation ofthe connected ports of the MCU and RCU can be different. However, when the MCU and RCU areconnected to the same host, controller emulation of the host-connected ports of the MCU and RCU must bethe same.

Volume pairs (P-VOLs and S-VOLs)

Continuous Access XP performs remote copy operations for logical volume pairs you create. EachContinuous Access XP pair consists of one primary volume (P-VOL) and one secondary volume (S-VOL),which can be in the same disk array (synchronous only) or different disk arrays. The Continuous Access

XP P-VOLs are primary volumes (LUs) containing original data, and the Continuous Access XP S-VOLs aresecondary or mirrored volumes (LUs) containing replicated or duplicate data. Volumes are copied on anOpen volume basis, and logical volumes should have the same format and capacity (SCSI path definitionis required). During normal Continuous Access XP operations, the P-VOL remains available to all hosts atall times for read and write I/O operations. During normal Continuous Access XP operations, the RCUrejects all host-requested write I/Os for the S-VOLs. The S-VOL write enable option allows write access toan S-VOL while the pair is split, and uses the S-VOL and P-VOL cylinder maps to resynchronize the pair(see S-VOL write option on page 20).

Continuous Access XP supports basic logical unit (LU) types available on the XP1024/XP128. ContinuousAccess XP also supports LU Size Expansion (LUSE), Custom Volume Size (CVS), and Cache LUN XPfeatures, ensuring that all user data can be backed up or duplicated. See Logical unit (LU) types onpage 31 for further information about LU requirements and support.

Continuous Access XP supports a maximum of 8,192 Continuous Access XP pairs (entire RCU). WhenContinuous Access XP pairs include size-expanded LUs, the maximum number of pairs decreases. Whenthe RAID Manager command device is defined, the maximum number of Continuous Access XP pairs inthe XP1024 is 8,191 (4,095 in the XP128).

Continuous Access XP supports the following RAID level configurations.

Continuous Access XP Asynchronous consistency groups

A Continuous Access XP Asynchronous consistency group is a user-defined set of volume pairs acrosswhich update sequence consistency is maintained and ensured at the remote site. Each ContinuousAccess XP Async volume pair must be assigned to a consistency group. Continuous Access XP canconfigure up to 128 consistency groups (0-7F) for each MCU and provides group-based operations forconsistency groups (for example, split and resync group). Use consistency groups to maintain updatesequence consistency for databases spanning multiple volumes, allowing immediate database recovery at

Table 3 Continuous Access XP supported RAID level configurations

For P-VOL For S-VOL

RAID 1 RAID 1

RAID 5 RAID 5

RAID 1 RAID 5

RAID 5 RAID 1


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the remote site when needed. See Continuous Access XP Asynchronous consistency group operationson page 23 for further information.

Only Continuous Access XP Asynchronous pairs belonging to the same CLPR can be allocated to oneContinuous Access XP consistency group. For more information about CLPRs, see the HP StorageWorksXP Disk/Cache Partition user guide.

Remote copy connections

Remote copy connections are physical paths MCUs use to communicate with RCUs. The number ofphysical paths in the MCU is limited to eight per logical CU image. MCUs and RCUs are connected viaFibre Channel interface or serial (ESCON) interface cables.

When Fibre Channel interface connections are used, switches are required for distances greater than0.5 km (1,640 feet). Distances up to 1.5 km (4,920 feet, 0.93 miles) are supported with dual switchesutilizing shortwave connections. Distances up to 10 km (6.2 miles) are supported using dual switcheswith longwave connections. Distances up to 30 km (18.6 miles) are supported using dual switcheswith longhaul connections. Distances up to 100 km are supported by using dual switches withDWDM. See Fibre Channel remote copy connections on page 34 for further information aboutinstalling and configuring Fibre Channel remote copy connections.

When serial interface connections are used, ESCON directors (ESCDs) and/or ESCON repeaters arerequired for distances greater than 3 km (1.9 miles). Continuous Access XP operations can beperformed at distances of up to 43 km (26.7 miles) using standard ESCON support. Long-distance

solutions are provided, based on user requirements and workload characteristics, using approvedprotocol converters and communication lines, such as T1/T3/ATM. See Serial remote copyconnections on page 35 for further information about installing and configuring serial remote copyconnections.

The MCU-to-RCU remote copy configuration for Continuous Access XP Asynchronous has differentrequirements than the Continuous Access XP Synchronous configuration, as follows:

Continuous Access XP Synchronous supports 1-to-n and n-to-1 remote copy connections (n4). OneMCU can be connected to as many as four RCUs. One RCU can be connected to as many as fourMCUs (one MCU/RCU = one physical CU, including all sixteen CU images).

Continuous Access XP Asynchronous supports 1-to-1 remote copy connections within the sameconsistency group. P-VOLs and S-VOLs of pairs in a consistency group must be within one physical

MCU and one physical RCU. This configuration ensures backup integrity for a data set spread acrossmultiple volumes within one XP1024/XP128 (such as large databases).

Continuous Access XP Asynchronous 1-to-n and n-to-1 (n 4) configurations (one main disk array andmultiple remote disk arrays) are valid for Continuous Access XP Asynchronous if all volumes belongingto a single consistency group are only 1-to-1.

With direct connect Fibre Channel (no switch), fibre remote copy supports 1-to-1 remote copyconnections. One XP1024/XP128 as an MCU can be connected to only one XP1024/XP128 as anRCU via optical fibre cables. For CU images within one XP1024/XP128, 1-to-4 and 4-to -1 remotecopy connections are supported via direct connects or an FC switch.

HP strongly recommends you establish at least two independent remote copy connections (one per cluster)between each MCU and RCU to provide hardware redundancy for this critical communications path.

Initiator ports and RCU target portsInitiator ports are dedicated Fibre Channel interface ports on the main disk array (MCU) to which RCUs(RCU target ports) are connected. Initiator ports connect to RCUs to send write I/O operations directly toRCUs. You can configure Fibre Channel interface ports of the XP1024/XP128 as initiator ports. Use thePort Change operation (see Port change operation on page 65) to change the configuration of theXP1024/XP128 Fibre Channel ports (ordinary target port, initiator port, or RCU target port) as needed.

NOTE: Initiator ports cannot communicate with hosts, but are used exclusively as Continuous Access XPtalkers. Ordinary target ports can be used only for host connect (not for Continuous Access XP).


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RCU target ports are (Continuous Access XP) dedicated Fibre Channel interface ports on the remote diskarray (RCU) to which MCUs (initiator ports) are connected. You can configure Fibre Channel interfaceports of the XP1024/XP128 as RCU target ports. For performance reasons, RCU target ports should notbe shared with host connects.

Remote control ports (RCPs) and local control ports (LCPs)

Remote control ports (RCPs) are dedicated serial interface ports on the MCU to which RCUs areconnected. RCPs emulate host processor channels, enabling MCUs to send write I/O operations directlyto RCUs. RCPs support the dynamic switching capability provided by ESCDs. You can configure serial

interface ports of the disk array as RCPs. Use Continuous Access XP to change the configuration of diskarray serial ports (LCP or RCP) as needed (see Port change operation on page 65).

Local control ports (LCPs) are used for host processor channel interfaces. All serial interface ports on thedisk array have a default setting of LCP. An RCU port connected to an MCU must be in LCP mode toreceive remote copy I/O operations from the MCU.

Two or more RCPs must be configured before you can add RCUs and create Continuous Access XPvolume pairs. RCPs cannot communicate with host processor channels and are dedicated to ContinuousAccess XP operations. Host channel interface paths must be connected to other interface ports on the diskarray.

Serial interface ports, 1S-1Z and 2S-2Z, cannot be specified as RCPs.

CHA package ports added to DKA slots cannot be specified as RCPs.Command View XP management station or XP Remote Web Console

The Command View XP management station is attached to the XP1024/XP128 on the internal LAN via aTCP/IP connection. The Command View XP management station communicates with each attachedXP1024/XP128.

The Command View XP management station at the primary site must be connected to the MCU of eachContinuous Access XP pair. A second Command View XP management station should be installed at theremote site and connected to the RCUs. With another Command View XP management station at theremote site, you can modify the Continuous Access XP Asynchronous options of the RCU (for example,pending update data rate or offloading timer) and access the Continuous Access XP S-VOLs (for example,to perform media maintenance). To perform Continuous Access XP operations in the reverse direction

from the remote site to the primary site (for example, disaster recovery), Continuous Access XP simplifiesand expedites this process.

Alternatively, you can access XP Remote Web Console directly on the MCUs and RCUs to manage theirrespective disk arrays.

Host failover software

Host failover software, which transfers information between host servers at primary and remote sites, is acritical component of any disaster recovery effort. Host failover is configured using the host failoversoftware product for the platform (such as Microsoft Cluster Server or HP Cluster Extension XP),depending on your installation requirements and standards. Command View XP or XP Remote WebConsole does not provide host failover functions.

When Continuous Access XP is used as a data migration tool, host failover is recommended but notrequired. When Continuous Access XP is used as a disaster recovery tool, host failover is required toensure effective disaster recovery operations. When a Continuous Access XP pair is suspended due to anerror condition, the MCU generates sense information that should be transferred to the remote site via hostfailover software for effective disaster detection and recovery.


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Remote copy operationsThere are two types of Continuous Access XP remote copy operations: initial copy and update copy.

Figure 3 Remote copy operations

Initial copy operations

Initial copy operation synchronize P-VOLs and S-VOLs independently of host I/O processes. Initial copyoperations are the same for Continuous Access XP Sync and Continuous Access XP Async pairs.Continuous Access XP initial copy operations occur when adding a pair (paircreate) or resuming asplit/suspended pair (pairresync). When a new pair is created, the entire contents of the P-VOL arecopied to the S-VOL cylinder by cylinder, except for diagnostic and unassigned alternate tracks. You canselect No Copy for the Initial Copy field of the initial copy parameters, which copies only cylinder #0 to

the S-VOL. If No Copy is selected, you are responsible for ensuring that P-VOLs and S-VOLs are alreadyidentical. The MCU cannot verify the contents of volumes. When a split/suspended pair is resumed(pairresync), only cylinder #0 and out-of-sync cylinders (updated by write I/Os during split/suspension)are copied to the S-VOL. When the Continuous Access XP S-VOL write enable function is used, the RCUtracks S-VOL updates and sends the S-VOL cylinder bitmap to the MCU when the split pair is resumed. Inthis case the MCU merges the P-VOL and S-VOL bitmaps to identify out-of-sync cylinders.

For additional flexibility, Continuous Access XP provides the following options for initial copy:

Use the Initial Copy Pace field of the initial copy parameters to specify how many tracks theContinuous Access XP initial copy operation copies simultaneously when creating/resuming aContinuous Access XP pair. This option can only be specified using Continuous Access XP.

Use the Priority field of the initial copy parameters to specify the order in which initial copy operations

are performed when creating/resuming multiple Continuous Access XP pairs. This option can only bespecified using Continuous Access XP.

Use the Maximum Initial Copy Activity option to specify maximum number of concurrent initial copyoperations each MCU can perform (not pair-specific). This option can only be specified usingContinuous Access XP.

Update copy operations

Update copy operations occur when the host issues a write I/O operation to the P-VOL of an establishedContinuous Access XP pair. Update copy operations duplicate P-VOL write I/Os at the S-VOL to keep thevolume pair synchronized. Continuous Access XP provides two modes for update copy operations:synchronous and asynchronous. Update copy mode is specified when you add a Continuous Access XPpair and is unchangeable for the life of the pair.

For synchronous update copy mode, the MCU ensures the P-VOL and S-VOL are synchronized at all times.When using fence level data, the MCU does not return final ending status for the P-VOL write I/O untilthe outcome of the P-VOL write and its associated update copy operation at the RCU are known. Forsynchronous mode, the MCU starts the update copy operation when it receives:

A write command whose data length is short enough not to pass the track-end

Write data to the track-end, whose total length is long enough to pass the track-end

Write data to the last track for the command

NOTE: No matter how long the write data is, update copy is executed for each track.


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For asynchronous update copy mode, the MCU stores P-VOL updates with additional control informationin cache, and sends updates and control information to the RCU completely independent of host I/Oprocesses. These updates and their associated control information are called recordsets. The RCU storesrecordsets in cache and performs updates to S-VOLs in the same order as they were performed at MCUsaccording to the sequence information stored in the recordset. For more information on recordsetoperations, see Continuous Access XP Asynchronous recordset operations on page 21.

Priority of initial and update copy: In both Continuous Access XP Synchronous and Continuous Access XPAsynchronous, update copy has higher priority than initial copy. However, initial copy is executed basedon copy pace (3 or 15 tracks). Therefore, update copy must wait this interval if initial copy is beingexecuted. For example, if the copy pace is 15 tracks, the update copy may wait up to 15 tracks (1cylinder). For Continuous Access XP Asynchronous, update copy is executed asynchronously, but thesame scheduling conflict can occur between the asynchronous update copy (write recordset) and initialcopy.

Read and write I/O operations for Continuous Access XP volumes

When an MCU receives a read command for a Continuous Access XP P-VOL, the MCU completes theread from the P-VOL. The MCU will not read the Continuous Access XP S-VOL over the link if a failurerendered the P-VOL inaccessible.

When an MCU receives a write command for a Continuous Access XP Synchronous P-VOL with COPYstatus and the track has already been copied to the S-VOL, the MCU performs a synchronous update copy

operation to complete the write at the S-VOL. When an MCU receives a write command for a ContinuousAccess XP Asynchronous P-VOL with COPY status and the track has already been copied to the S-VOL, theMCU performs an asynchronous update copy operation.

When an MCU receives a write command for a Continuous Access XP P-VOL with PAIR status, theuser-selected update copy mode (synchronous or asynchronous) determines the sequence of events asfollows:

Synchronous Mode: The MCU performs the write operation on the P-VOL, starts the update copyoperation for the S-VOL, and reports final ending status to the host only after results of the update copyoperation are known. If the P-VOL write or S-VOL update copy operation fails, the MCU reports a unitcheck, and the host system and application program regard that write operation to the P-VOL asfailed.

Asynchronous Mode: The MCU completes P-VOL write operations independently of the associatedupdate copy operations at the S-VOL. The RCU manages the S-VOL updates according to recordsetinformation and maintains sequence ordered data consistency for the S-VOLs. If the P-VOL writeoperation fails, the MCU reports a unit check and does not create the Continuous Access XPasynchronous recordset for this operation. If the update copy operation fails, the RCU optionallysuspends the affected pair or all pairs in the consistency group, depending on the type of failure.When the suspended pair or group is resumed (pairresync), the MCU and RCU negotiate theresynchronization of the pairs. See Continuous Access XP suspend types on page 28 for furtherinformation about suspended Continuous Access XP Async pairs.

The RCU does not allow a Continuous Access XP S-VOL to be online (mounted) during normal ContinuousAccess XP operations and rejects all host-requested write I/O operations for an S-VOL. The specialContinuous Access XP S-VOL write enable option enables write access to an S-VOL while the pair is split

(see S-VOL write option on page 20). The S-VOL write option can be enabled only when you split thepair from the MCU.

To reduce overhead associated with Continuous Access XP remote copy operations, the XP1024/XP128uses a special write command that is allowed only for Continuous Access XP initial and update copyoperations. This Continuous Access XP command transfers control parameters and FBA-format data,which includes consecutive updated records in each track, using a single write operation. This capabilityeliminates overhead required for performing FBA-to-CKD and CKD-to-FBA conversions.

S-VOL write option

Continuous Access XP provides an S-VOL write option that enables write access to the S-VOL of a splitContinuous Access XP pair. The S-VOL write option can be selected during the pairsplit-r operation andapplies only to the selected pairs. The S-VOL write option can be accessed only when you are connected


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to the MCU. When you resync a split Continuous Access XP pair that has the S-VOL write option enabled,the RCU sends the S-VOL cylinder bitmap to the MCU, and the MCU merges the P-VOL and S-VOLbitmaps to determine which cylinders are out-of sync. This ensures proper resynchronization of the pair.

Continuous Access XP Asynchronous recordset operationsContinuous Access XP Asynchronous recordsets contain P-VOL updates and associated controlinformation, including sequence number of the P-VOL update, which enables the RCU to maintain updateconsistency of S-VOLs. Continuous Access XP Recordset operations include:

Creating and storing recordsets at the MCU on page 21 Sending recordsets to the RCU on page 21

Storing recordsets at the RCU on page 21

Selecting and settling recordsets at the RCU on page 22

Types of recordsets on page 22

Inflow control of recordsets on page 22

Creating and storing recordsets at the MCU

When an MCU performs an update (host-requested write I/O) on a P-VOL, the MCU creates a recordsetcontaining the updated record, sequence number, record location (device, cylinder, track, and recordnumber), and record length. Recordsets are queued in cache storage of the MCU and sent to the RCU

independent of host I/O processes. The RCU utilizes sequence number information in the recordsets toupdate S-VOLs in the same order as P-VOLs.

The sequence number indicates the number of recordsets the MCU created for each consistency group.Recordset information, except for updated records, is stored and queued in an area of cache known assidefile cache (see Inflow control of recordsets on page 22).

NOTE: Continuous Access XP Asynchronous operations continue uninterrupted if the disk array rebootsor the disk arrays internal Service Processor (SVP) fails.

Sending recordsets to the RCU

The MCU sends asynchronous Continuous Access XP recordsets to the RCU in a manner similar toContinuous Access XP synchronous updates. The MCUs initiator ports act as host processor channels andissue special I/O operations, called remote I/Os (RIOs), to the RCU. The RIO transfers recordsets in FBAformat (not CKD) using a single channel command, eliminating overhead associated with FBA-CKDconversion and thus providing more efficient data transfer. The MCU can send several recordsets using asingle RIO, even if their sequence numbers are not contiguous. Therefore, recordsets are usually sent tothe RCU in a different order than the arrivals at the MCU. The RCU ensures that records are applied to theS-VOLs in the correct sequence. This method of remote I/O provides the most efficient use of MCU-to -RCUlink resources.

The parameter length and detailed specification of the Continuous Access XP Asynchronous channelcommand are different than for Continuous Access XP Synchronous RIOs. You must ensure that yourchannel extenders support this command. For further details, contact your HP account support

representative.

Storing recordsets at the RCU

The RCU maintains queues to control storing recordsets in the sidefile and committing updated records inthe S-VOLs. The RCU queuing mechanism for Continuous Access XP Async uses sequence numbersprovided by the MCU to check for missing updates.

The MCU does not remove the sidefile entry for a recordset from its cache until it receives an I/Ocompletion signal (device end) from the RCU. This is true even if the MCU and RCU are connected via achannel extender product. If a recordset is lost in transmission from the MCU to the RCU, the MCUscylinder bitmap ensures that the missing recordset is identified and resent to the RCU.


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Selecting and settling recordsets at the RCU

The RCU selects recordsets to be promoted to formal data (or settled) as follows:

1. The RCU checks for a valid entry at the top of each queue in the consistency group. If the top of anyqueue is empty (recordset not yet received), the RCU waits for that entry.

2. When the top of each queue contains a valid entry (recordset), the RCU selects the entry with theearliest sequence number, and settles that recordset.

3. The RCU repeats this process to select and settle Continuous Access XP Asynchronous recordsets.

Figure 4 illustrates recordset selection and settling at the RCU. In this example, the top of the queuecontains a valid entry: S1. The RCU selects recordset S1 to be settled, because S1 is the earliest sequencenumber. When S1 is removed from the MCU queue, recordset S2 becomes the top entry, but it is empty.When recordset S2 arrives the RCU selects S2 as the next recordset to be settled. The recordset the RCUselects is marked as host-dirty and treated as formal data. The RCU settles the updated records in therecordset as follows:

If the corresponding track is in cache (track-hit), updated records in the recordset are copied to theexisting cached track, and cache space for the sidefile is released.

If the corresponding track is not in cache (track-miss), the RCU changes the cache designation of thesidefile to formal data. Data is not physically moved.

Figure 4 Selecting and settling Continuous Access XP Async recordsets at the RCU

Types of recordsets

In addition to host update recordsets, the MCU passes control information to the RCU in specialnon-update recordsets. These special recordsets indicate when volume pair status changes, indicate whenan MCU power-off sequence is initiated, and maintain sequence numbers in periods of low host activities.

Inflow control of recordsets

As described in previous sections, both the MCU and RCU create sidefiles for storing Continuous AccessXP Asynchronous recordsets. Because sidefiles occupy exclusive space in cache, both the MCU and RCUperform inflow control to prevent an overload of the disk arrays cache resources. The XP1024/XP128uses certain parameters for Continuous Access XP Asynchronous cache inflow control. Use the ContinuousAccess XP Async Option pane to modify the following parameters (see Asynchronous copy option onpage 70):

Pending Update Data Rate (%): Sidefile (Continuous Access XP) threshold = maximum cache %available for use by Continuous Access XP Asynchronous sidefiles.

Offloading Timer (sec.): Maximum time between Continuous Access XP Async recordset transfers.

I/O Delay Start (%): Maximum amount of cache for starting I/O inflow control.

I/O Delay Increase (%): Maximum amount of cache for starting to strengthen control over I/O inflow.


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Inflow control by MCU

When the amount of MCU sidefile cache reaches the user-specified threshold (I/O delay start), the diskarrays I/O response is delayed. When the amount of MCU sidefile cache reaches the user-specifiedthreshold (I/O delay increase), the disk arrays I/O delay starts increasing. If the MCU cannot send arecordset to the RCU within the user-specified offloading timervalue, the MCU suspends all affectedContinuous Access XP Async volume pairs and resets the SCP condition to avoid hanging up the system.

Inflow control by RCU

When the amount of RCU sidefile cache reaches the user-specified threshold, the RCU responds withchannel-command-retry requests to the RIO commands that transfer recordsets from the MCU. The RCUaccepts only the recordset with the sequence number required to continue settling pending recordsets. Ifthe RCU cannot settle a recordset within the user-specified offloading timer value, the RCU suspends allContinuous Access XP Asynchronous volume pairs and resets the channel-command-retry condition toavoid hanging up the MCU.

Table 4 shows sidefile threshold values for Continuous Access XP Asynchronous operations and writepending operations and describes actions occurring when each threshold is reached.

HP Cache LUN XP operations might decrease total amount of cache available for Continuous Access XPAsynchronous operations, but they do not directly affect sidefile cache usage. Available cache is theamount of physical cache memory installed on the disk array minus any cache reserved for the HP CacheLUN XP feature.

If you do not want to control inflow into a sidefile, specify the value of the Pending Update Data Rate forthe I/O Delay Start and I/O Delay Increase, and specify 0 seconds for the Offloading Timer.

Continuous Access XP Asynchronous consistency group operationsContinuous Access XP Asynchronous consistency groups maintain update sequence consistency across anaggregated data set spanning a group of volumes. P-VOLs and S-VOLs of the pairs in a consistency groupmust be located within one physical MCU and one physical RCU (1-to-1 requirement). Continuous AccessXP consistency group operations include:

Group options

Group consistency time

Group operations

Table 4 Sidefile threshold values for Continuous Access XP Asynchronous operations and write pendingoperations

Operation Thresholds Actions

Continuous AccessXP Asynchronous

I/O Delay Start (threshold) = 30%

Use Continuous Access XP to adjust threshold todesired value between 0 and 70% in 1%increments. Specify a value not exceeding thevalue of I/O Delay Increase, and Sidefile threshold.

MCU reaches threshold: I/O delaystarts. If sidefile threshold is setbetween 0 and 30%, influence tothe I/O delay is kept low.

RCU reaches threshold: No action.


I/O Delay Increase (threshold) = 40%

Use Continuous Access XP to adjust threshold todesired value between 0 and 70% in 1%increments. Specify a value within the range of theI/O Delay Start threshold and Sidefile threshold.

MCU reaches threshold: I/O delayincreases. If sidefile threshold is setbetween 0 and 30%, influence tothe I/O delay is kept low.

RCU reaches threshold: No action.


Sidefile threshold = 50%

Use Continuous Access XP to adjust threshold(30, 40, 50, 60, or 70%).

MCU reaches threshold: I/O delay.

RCU reaches threshold: Commandretry to MCU.

Write Pending [write pending] / [avail cache - sidefile] = 70% Command retry.


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Group options

Continuous Access XP provides the following options for each consistency group: copy pending timeoutand RCU ready timeout. These options are selected when you add a group, and can be modified onlywhen the group does not contain any P-VOLs in the MCU.

Copy pending timeout

This group option specifies maximum delay allowed for Continuous Access XP Async copy operations.The RCU suspends all S-VOLs in the group when:

The RCU has not had any communications from the MCU within the specified time. This situation mightindicate a disaster or failure at the primary site.

The RCU has received recordsets from the MCUs but has not been able to settle a particular recordsetwithin the specified time. This situation might indicate the RCU does not have enough resources tohandle remote copy and I/O workloads.

RCU ready timeout

This group option specifies maximum delay allowed for re-establishing MCU-RCU communicationsfollowing MCU power-off. During MCU power-on, the MCU re-establishes communications with allregistered RCUs. If the MCU cannot re-establish communications with an RCU within the specified time,the MCU suspends all affected Continuous Access XP Asynchronous volume pairs.

Group operationsContinuous Access XP Asynchronous provides the following group-based operations to simplify andexpedite disaster and failure recovery procedures:

Group operations at the MCU:

Split (pairsplit-r) all pairs in a consistency group. See Splitting Continuous Access XP pairs(Pairsplit-r) on page 85 for a description of the Suspend Range-Group pairsplit-r option.

Resume (pairresync) all split or suspended pairs in a group. See Resuming Continuous Access XPvolume pairs (Pairresync) on page 88 for a description of the Continuous Access XP ResumeRange-Group pairresync option.

Delete (pairsplit-S) all pairs in a group. See Deleting Continuous Access XP volume pairs(Pairsplit-S) on page 90 for a description of the Delete Range-Group pairsplit-S option.

Group operations at the RCU: Split (pairsplit-r) all pairs in a consistency group. See Splitting Continuous Access XP pairs

(Pairsplit-r) on page 85 for a description of the Suspend Range-Group pairsplit-r option.

Delete (pairsplit-S) all split or suspended pairs in a consistency group except inconsistent pairs. SeeDeleting Continuous Access XP volume pairs (Pairsplit-S) on page 90 for a description of theDelete Range-C/T pairsplit-S option.

Delete (pairsplit-S) all pairs in a group regardless of their consistency status. See DeletingContinuous Access XP volume pairs (Pairsplit-S) on page 90 for a description of the DeleteRange-Group pairsplit-S option.

Continuous Access XP also provides the Error Level pair option (see Continuous Access XP initial copyand pair options of the Paircreate pane on page 84), which triggers automatic suspension of an entire

consistency group. When a Continuous Access XP Async pair is suspended due to failure (notuser-requested), this Continuous Access XP pair option determines whether all pairs in the sameconsistency group are also suspended. If you selected the Group error level for the Continuous Access XPAsync pair, all pairs in the same group are suspended. If you selected the LU error level, only the affectedContinuous Access XP Async pair is suspended.

The Error Level pair option is very important for managing Continuous Access XP Asynchronous groupsand planning disaster recovery. The Group error level should be selected for all Continuous Access XPAsync volumes essential to disaster recovery. Suspended Continuous Access XP Async S-VOLs with the LUerror level should not be used for disaster recovery because they are not consistent with the rest of thevolume group.


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Continuous Access XP volume pair statusContinuous Access XP displays pair status for each volume in the selected logical CU image (CUI) of theconnected XP1024/XP128. Table 5 describes Continuous Access XP pair status descriptions. The MCUmaintains the status of the P-VOL and can change the pair status of the P-VOL and S-VOL. The RCUmaintains the status of the S-VOL and can change the pair status of the S-VOL but not the P-VOL. The MCUdetects when the RCU changes the S-VOL status (if path status is normal) and changes the P-VOL statusaccordingly. You can display detailed pair status information using the Command View XP or XP RemoteWeb Console GUI (Continuous Access XP Pairdisplay pane) or UNIX/PC server host (RAID Manager

Pairdisplay command).A volume not assigned to a Continuous Access XP pair has status SMPL. When a Continuous Access XPpair is started, the MCU changes the status of the P-VOL and S-VOL to COPY. When the initial copyoperation is complete, the MCU changes the status of both volumes to PAIR. When you split a ContinuousAccess XP pair (pairsplit-r), the MCU/RCU changes the status of the P-VOL and S-VOL to PSUS (if pathstatus is normal). When a pair is suspended due to an error condition, the MCU/RCU changes the P-VOLand S-VOL status to PSUE (if path status is normal). When you delete a pair from the MCU (pairsplit-S), theMCU changes the status of the P-VOL and S-VOL to SMPL (if path status is normal). When a pair is deletedfrom the RCU, the RCU changes the S-VOL status to SMPL, and the MCU detects the pair deletion (if pathstatus is normal) and changes the P-VOL status to PSUS.

When a Continuous Access XP pair is split or suspended, the MCU generates a service informationmessage (SIM) to notify the hosts. This SIM results in a trap indicating the reason for suspension.

Continuous Access XP LUSE pair status

For Continuous Access XP LUSE pairs only, PDUB (dubious) status indicates the status of the ContinuousAccess XP LUSE volume pair is COPYor PAIR, but the status of one or more individual LDEV pairs withinthe Continuous Access XP LUSE pair is SMPL or PSUE (due to some error condition).

Continuous Access XP Asynchronous pair status

The Suspending and Deletingtransitional states occur when a request to change Continuous Access XPAsync pair status is accepted, but the change to the requested status (PSUS, PSUE, or SMPL) is not yetcomplete. These states are not reported to the host. For Suspending, you and the MCU can request thestatus change. For Deleting, only you can request the status change. If you requested the status change,the final status is reported at the end of the transition. If an error caused the status to change to PSUE, the

suspended status is reported at the beginning of the transition.

Table 5 Continuous Access XP Asynchronous pair status descriptions

Pair status Description P-VOL access S-VOL access

SMPL(simplex)

Volume is not currently assigned to a ContinuousAccess XP volume pair. When this volume isadded to a Continuous Access XP pair, its statuschanges to COPY.

Read/write Read/write

COPY Initial copy operation for this pair is in progress.This pair is not yet synchronized. When initialcopy is complete, the status changes to PAIR.

Read/write Read only

PAIR Pair is synchronized. Updates to the P-VOL areduplicated on the S-VOL.



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PSUS(pair suspended-split)

(see Table 6 onpage 27 for splittypes)

Pair is not synchronized because you split this pair(pairsplit-r) or deleted this pair from the RCU(pairsplit-S). For Continuous Access XP Asyncpairs, the MCU and RCU track recordsetsdiscarded during the pairsplit-r operation. While apair is split, the MCU and RCU track P-VOL and

S-VOL cylinders updated.

When you split a pair from the MCU, the MCUchanges the status of the P-VOL and S-VOL toPSUS. When you split a pair from the RCU, theRCU changes the status of the S-VOL to PSUS. TheMCU detects this (if path status is normal) andchanges the P-VOL status to PSUS.

When you delete a pair from the RCU, the RCUchanges the S-VOL status to SMPL. The MCUdetects this (if path status is normal) and changesthe P-VOL status to PSUS. You must delete the pairfrom the MCU to change the P-VOL status to SMPL.

Read/write Read only;Read and write,if write enablesplit option isselected.

PSUE(pair suspended-error)

(see the table inTable 6 on page 27for suspend types)

Pair is not synchronized because the MCU or RCUsuspended the pair due to an error condition. ForContinuous Access XP Async pairs, the MCUand RCU track recordsets discarded during thesuspension operation. The MCU tracks P-VOLcylinders updated while the pair is suspended.

For Continuous Access XP Synchronous pairs, ifthe MCU cannot keep the pair synchronized forany reason, the MCU changes the status of theP-VOL and S-VOL (if possible) to PSUE.

For Continuous Access XP Asynchronous pairs, ifthe MCU detects a suspension condition(see

Continuous Access XP Asynchronous suspensionconditions on page 29), the MCU changes theP-VOL and S-VOL status (if possible) to PSUE.

For Continuous Access XP Asynchronous pairs, ifthe RCU detects a suspension condition(seeContinuous Access XP Asynchronous suspensionconditions on page 29), the RCU changes theS-VOL status to PSUE, and the MCU detects this (ifpath status is normal) and changes the P-VOLstatus to PSUE.

Read/write;Read only iffenced.

Read only

Pair Status for Continuous Access XP LUSE volumes only:

PDUB Continuous Access XP pair consists of LUSEvolumes (for example, OPEN3*n), and anindividual LDEV within this Continuous AccessXP LUSE pair failed due to some error condition.The status of the Continuous Access XP LUSEvolume is PAIR or COPY, and the status of one ormore LDEV pairs is PSUE or SMPL.


Table 5 Continuous Access XP Asynchronous pair status descriptions (continued)

Pair status Description P-VOL access S-VOL access


27/108


Continuous Access XP split types (PSUS)

Table 6 describes Continuous Access XP split types. You can split a Continuous Access XP pair at any timeafter the initial copy operation is complete. You must split a Continuous Access XP pair to perform media

maintenance on the P-VOL or change the S-VOL (S-VOL write enable).When you split a Continuous Access XP Synchronous pair, the MCU ensures synchronization bycompleting any pending update copy operation before changing the status to PSUS. After the pair statuschanges to PSUS, the MCU stops performing update copy operations to the S-VOL and may or may notcontinue accepting write I/Os for the P-VOL, depending on the P-VOL fence level and pairsplit-r options. Ifthe P-VOL accepts write operations while the pair is split, the MCU tracks P-VOL cylinders updated. If youenabled the S-VOL write option when you split the pair, the RCU tracks S-VOL cylinders updated while thepair is split. When the pair is resumed (pairresync), the RCU sends the S-VOL cylinder bitmap to the MCU,and the MCU merges the P-VOL and S-VOL bitmaps to determine which cylinders are out-of-sync.

When you split a Continuous Access XP Asynchronous pair, the MCU and RCU ensure synchronization bycompleting or discarding pending update copy operations according to the user-specified drain/purgepairsplit option. The MCU and RCU track recordsets discarded during the pairsplit operation. After thepair status changes to PSUS, the MCU stops performing recordset operations for the pair, continuesaccepting write I/Os for the split Continuous Access XP Async P-VOL, and tracks P-VOL cylin

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