Logical Standby Database for Reporting

Mark Bole

NoCOUG Nov 10, 2005

Introduction

Mark Bole

Independent Consultant

Oracle, Unix, Perl since 1991

http://www.bincomputing.com

Today’s Session

• DataGuard Logical Standby — going outside the DG box

• What is Logical Standby?

• How to set it up

• Reporting/Batch: refresh cycle, materialized views, maintenance

DataGuard vs. Streams From the Oracle docco:

“While Streams and Data Guard do share some common underlying […] technology, they are both independent features that are built to solve different business needs. [see references]

“Oracle Data Guard is designed for protecting from data failure and disasters.

“Streams is designed for information sharing and distribution but can also provide a very efficient high availability solution.”

Logical Standby Product Placement?

Integration

8i

9i

10g

High Availability

Oracle Streams Oracle Data Guard –

SQL Apply (Logical Standby)

Basic Replication

Advanced Replication

Basic readable standby database

Oracle Data Guard – Redo Apply (Physical Standby)

Logical Standby Product Placement?

Integration

8i

9i

10g

High Availability

Oracle Streams Oracle Data Guard –

SQL Apply (Logical Standby)

Basic Replication

Advanced Replication

Basic readable standby database

Oracle Data Guard – Redo Apply (Physical Standby)

Why Not Logstdby for HA?

“Parity, one-to-one-ness, having a failover environment that is a mirror image of the production [site]. That is the ‘ideal’ situation.”

http://asktom.oracle.com

Too Many Ways for the Logical Standby to deviate from the primary — intentional or otherwise!

“Bugs” – A Real-Life StoryThe following is an excerpt from a recent posting on the oracle-l list.Need some help or opinions regarding Oracle logical standby database.

Logical standby, version 10, release x, patch x. Primary and standby are tightly coupled (maximum availability mode). [...]

2) From time to time, standby breaks, but this seems due mostly to schema changes [...]

3) DB Guard leaks memory on the primary. This was confirmed via the OS, not V$-views. . Had to disable it. Not really happy about that. […]

5) Primary is not happy about unexpected standby restarts.[...]

6) To sum up: something's a bit shaky in my environmentt. Should I give up with maximum availability mode and reduce the database to maximum performance mode? I am interested to hear from others.

Logical Standby has a documented list of

restrictions*Unsupported Datatypes (partial list)

LONGLONG RAWBFILEROWIDuser-defined typesvarraysnested tables

Unsupported Tables, Sequences, and Views (partial list)

•Tables using data segment compression

•Index-organized tables

*Note: many removed in 10g

Robustness: less more

ASM

Evolution of Robustness

8i

9i

10g

RMAN

SQL ApplyRAC

Assumptions: Logstdby for Reporting

• Not running DG Manager/Broker• No intention of ever switching DG roles • Log transport MAXIMUM PERFORMANCE mode• Implies existence of separate Physical Standby for

“real” recovery• NOARCHIVELOG mode (all report/batch data can be

re-created if necessary)• Service Level less than 24 x 7 (planned maintenance

outages)• Not running SQL Apply continuously

Today’s Session

• DataGuard Logical Standby — going outside the DG box

• What is Logical Standby?

• How to set it up

• Reporting/Batch: refresh cycle, materialized views, maintenance

The Goal:logical, not physical,

replication• Physical standby is an image copy of the

primary — every datafile block is the updated to match as of point in time.

• Other existing options for logical: Export / Import Traditional Advanced Replication Transportable tablespace (maybe)

DB Link

Previous Solution

Primary

Redo apply(once every 24 hours)

Physical Standby

Reporting Database

Daily Cycle:1. Close Physical Standby

2. Mount Physical Standby

3. Recover day's worth of redo

4. Open Physical Standbyread-only for rest of day

5. Run batch and reporting processes using dblink

6. Loop to step 1

DB Link

Previous Solution - Problems

Physical Standby (open read-only)

Reporting Database

• Need to close and re-open physical standby

• Two databases on same server creates inefficiencies

• Harder to tune distributed queries

• Cannot use MV logs in standby, hence cannot use MV's in reporting database

SQL Apply

“SQL Apply technology […] first transforms the redo data into SQL statements and then executes the generated SQL statements on the logical standby database.”

SQL Block-level changes

redo logminer SQL

Physical

Logical

GUI Log MinerI:\>Oracle\product\10.1.0\Client_1\BIN\oemapp.bat lmviewer

Select archived redo logs to mine

Example: schema in primarycreate user schema_blue

identified by xyz

default tablespace TESTDB_A

temporary tablespace temp

quota 100M on TESTDB_A

quota unlimited on temp;

grant create session, create table to schema_blue;

connect schema_blue/xyz@binc01.tree

CREATE TABLE test_table (name varchar2(50), value varchar2(50), timestamp date,constraint pk_test_table primary key (name) using index);

insert into test_table values ('test1', 'value1', sysdate);

insert into test_table values ('test2', 'value2', sysdate);

commit;

Logical Change Records

Logical Standby = Streams Made Simple

• Streams is configured from the bottom up — individual tables, schemas, capture processes, apply processes, queues

• Logical Standby is configured from the top down — start with entire database, then specify only what you don’t want

• Less muss, less fuss

Today’s Session

• DataGuard Logical Standby — going outside the DG box

• What is Logical Standby?

• How to set it up

• Reporting/Batch: refresh cycle, materialized views, maintenance

Logstdby Pre-requisites

• Enterprise Edition license

• Same operating system and platform architecture as primary

• Same RDBMS version (10g supports rolling upgrades)

• FORCE LOGGING at database level

Supplemental Logging “If you’re going to use supplemental logging, you need to be aware that you are actually asking for quite a lot of new information to be included in the redo stream… and all that extra information might just be enough to tip LGWR and ARCH over into serious performance problems.”

Howard J. Rogers, New Features in Oracle 9i

Much less of a problem if you have a unique or primary key on every table!

Create the Logstdby• Start with any kind of hot backup

• Mount or quiesce the primary (requires outage, restriction removed in 10g)

• EXECUTE DBMS_LOGSTDBY.BUILD to put the LogMiner dictionary into the redo stream

• Rename datafiles, online redo logs in standby• Reset database name — DBNEWID utility• Register archive logfile containing LogMiner

dictionary, start SQL Apply

My favorite LogStdby settings•INIT.ORAremote_archive_enable = receivestandby_archive_dest = '/opt/oracle/admin/binc01dg/stbyarch'

•DBA_LOGSTDBY_PARAMETERSDBMS_LOGSTDBY.APPLY_SET ('TRANSACTION_CONSISTENCY', 'NONE');DBMS_LOGSTDBY.APPLY_SET ('MAX_EVENTS_RECORDED', '2000');DBMS_LOGSTDBY.APPLY_SET ('RECORD_SKIP_DDL', 'FALSE');DBMS_LOGSTDBY.APPLY_SET ('RECORD_APPLIED_DDL', 'FALSE');DBMS_LOGSTDBY.APPLY_SET ('_EAGER_SIZE', 1000);

•alter database guard standby;

Today’s Session

• DataGuard Logical Standby — going outside the DG box

• What is Logical Standby?

• How to set it up

• Reporting/Batch: refresh cycle, materialized views, maintenance

DB Link

Previous Solution

Primary

Redo apply(once every 24 hours)

Physical Standby

Reporting Database

Daily Cycle:1. Close Physical Standby

2. Mount Physical Standby

3. Recover day's worth of redo

4. Open Physical Standbyread-only for rest of day

5. Run batch and reporting processes using dblink

6. Loop to step 1

The Logstdby Advantage

Primary

OLTP application

LogStdby

Reporting/Batch application

SCHEMA_REDTABLESINDEXESPL/SQL

SCHEMA_BLUETABLESINDEXESPL/SQL

SCHEMA_GREENTABLESINDEXESPL/SQL

SCHEMA_BLUETABLESINDEXESPL/SQL

SCHEMA_ORANGETABLESINDEXESPL/SQL

DG SQL Apply

The Logstdby Advantage

LogStdby

Reporting/Batch application

SCHEMA_BLUETABLESMV LOGSINDEXESPL/SQL

SCHEMA_ORANGETABLESINDEXESMATL_VIEWSPL/SQL

Now we can create Materialized View logs directly in the “source” schema without impacting the primary!

Guard Standby (read-only)

Controlling what is replicated-- workaround for bug in 9.2.0.5

exec DBMS_LOGSTDBY.SKIP('PROCEDURE', 'XYZ', '%', null);

exec DBMS_LOGSTDBY.SKIP('SCHEMA_DDL', 'VCS_MONITOR', '%', null);

exec DBMS_LOGSTDBY.SKIP('DML', 'VCS_MONITOR', '%', null);

-- NON_SCHEMA_DDL (for grants)

Example: MV logsschema_blue> select table_name from user_tables;

TEST_TABLE

schema_blue> delete from test_table where name = 'test1';

ORA-01031: insufficient privileges <= table is guarded

schema_blue> CREATE MATERIALIZED VIEW LOG on test_table

2 with sequence, primary key, rowid

3 (value, timestamp)

4 INCLUDING NEW VALUES;

Materialized view log created.

Example: Materialized Viewschema_orange> create materialized view mv_test_table 2 build immediate 3 refresh fast on demand 4 ENABLE QUERY REWRITE 5 AS 6 SELECT 7 count(*) cnt, 8 count(name) cnt_name, 9 tt.value, 10 trunc(tt.timestamp) trunc_timestamp 11 FROM 12 schema_blue.test_table tt 13 group by 14 tt.value, 15 trunc(tt.timestamp);

Materialized view created.

Fast Refreshable? Check!

schema_orange> SELECT OWNER,

2 MVIEW_NAME,

3 FAST_REFRESHABLE

4 FROM DBA_MVIEWS

5 /

OWNER MVIEW_NAME FAST_REFRESHABLE

-------------------- --------------- ------------------

SCHEMA_ORANGE MV_TEST_TABLE DIRLOAD_DML

Query Rewrite? Check!

schema_orange> exec DBMS_MVIEW.EXPLAIN_REWRITE ('select count(*) from schema_blue.test_table', 'mv_test_table');

PL/SQL procedure successfully completed.schema_orange> commit;

schema_orange> SELECT MV_OWNER, MV_NAME, QUERY, MESSAGE, PASS FROM REWRITE_TABLE ;[headings omitted]SCHEMA_ORANGE MV_TEST_TABLEselect count(*) from schema_blue.test_tableQSM-01033: query rewritten with materialized view,MV_TEST_TABLEYES

The Logstdby Advantage

LogStdby

Reporting/Batch application

SCHEMA_BLUETABLESMV LOGSINDEXESPL/SQL

SCHEMA_ORANGETABLESINDEXESMATL_VIEWSPL/SQL

Now we can create Materialized View logs directly in the “source” schema without impacting the primary!

Guard Standby (read-only)

SQL Apply — can be slow

• Redo contains uncommitted transactions

• Necessary overhead of logical vs. physical in general

• Be sure to read and follow Best Practices document

• Be prepared, in worst case, to recreate your Logical Standby for reporting!

Recover Perl scriptrecover_logstdby.pl - recover logical standby

Connect to database

alter database start logical standby apply

Die on error unless ORA-16105: Logical Standby is already running in background

While (BehindTime =

select

trunc( (newest_time - applied_time)*1440 )

from

dba_logstdby_progress)

if (BehindTime < specified recovery window)

done, successful

if (exceeded timeout)

done, unsuccessful, wake me up

End

alter database stop logical standby apply

Disconnect

ReferencesCreating a Logical Standby with Minimal Production Downtime

Note:278371.1

Oracle Data Guard Readme for SQL Apply Release 9.2.0.6

Note:286787.1

Oracle Data Guard Readme for SQL Apply Release 10.1.0.3

Note:304059.1

SQL Apply Best Practices (9i) http://otn.oracle.com/deploy/availability/pdf/DataGuardSQLApplyBestPractices.pdf

SQL Apply Best Practices (10g) http://www.oracle.com/technology/deploy/availability/pdf/MAA_WP_10gSQLApplyBestPractices.pdf

Oracle10g Data Guard SQL Apply Troubleshooting

Note:312434.1

ORA-1 Occurring on Logical Standby Note:257356.1

Synchronizing tables in a Logical Standby Database

Note:271455.1

Troubleshooting 9i Data Guard Network Issues

Note:241925.1

Streams and Data Guard Role Transitions http://www.oracle.com/technology/deploy/availability/pdf/MAA_WP_10gDataGuardRoleTransitionsStreams.pdf

Thank you!

Copy of presentation will be available at NoCOUG web site

Questions?