62884091 ims db fundamentals latest

8/13/2019 62884091 IMS DB Fundamentals Latest

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IMS / DB


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Table of Contents

Database SystemDefinition and Types

Introduction to IMS

IMS terminologies, organization, access methods

Control Blocks (DBD and PCB)

DBD - Definition, Functions and Macros PSB - Definition, Functions and Macros

How to run application program using DL/I

SSAsQualified and Unqualified

Command Codes

DL/I Calls

Status Codes


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Table of Contents (Contd..)

System service DL/I calls

Checkpoint Restart

Rollback calls

Exercises Case StudyHR Application


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4IMS Fundamentals

What is a Database System?

A system that allows multiple independent users to have concurrent access

to a central repository of information

Advantages

Centralized files for all applications

Elimination of duplicate space and effort

Single information source provides complete accurate informationprocessing

Concurrency and easily manageable.


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Types of DBMS

1.Hierarchical

A hierarchical database is a kind of database management system

that links records together in a tree data structure such that eachrecord type has only one owner, e.g. an order is owned by only one

customer. Hierarchical structures were widely used in the first

mainframe database management systems. However, due to their

restrictions, they often cannot be used to relate structures that exist

in the real world.


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Types of DBMS (Contd..)

2. Network

The network model is a database model conceived as a more flexiblealternative to the hierarchical model. Where the hierarchical modelstructures data as a tree of records, with each record having oneparent record and many children, the network model allows eachrecord to have multiple parent and child records, forming a lattice

structure.


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Types of DBMS (Contd..)

3. Relational

A relational database is organized into tables, in which data is

defined so that it can be reorganized and accessed in a number of

different ways without having to reorganize the database tables.


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What is IMS?

IMS (Information Management System) is IBM's hierarchical databaseproduct

Hierarchical Data base management system that supports the applicationprogram while processing data bases in batch or on-line environments.

IMS maintains an Inverted Tree Structure starting with the Root Segmentby ensuring that no segment has more than one parent.

The Hierarchy can go up to fifteen levels down.

The Hierarchy can represent up to 255 segment types


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Why IMS?

Advantages:

Large Volumes of Data can be handled

Faster Access of Data

Can be combined with DB2 for making data retrieval efficient (DB2 for

querying and IMS for processing)

Checkpoint restart feature available.

Limitat ions:

Not many tools for IMS compared to DB2 (File aid ~ file structure on pc)

Rigid design of IMS doesnt make it programmer friendly


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IMSComponents

Five componentsof IMS Environment

1. Database Management System Is the heart of IMS subsystem.Shared by many concurrent tasks. Data is stored in DASD. Applicationprograms access data by making DL/I calls.

2. DL/I (Data Language Interp reter) Is a set of program modulesinterfacing database and application program. The modules use standardoperating system access methods and a set of specialized access methodsto handle data transfers to and from the database. Is an interface languageused by the application program.


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IMSComponents (Contd..)

3. DL/I Contro l Block s- There are two main DL/I control blocks namely, Database Descriptor (DBD) which describes the databasestructure and Program Communication Block (PCB) which identifieshow the database may be accessed by the program.

4. Appl icat ion Program Are designed and coded by theprogrammers. Programs use a standard DL/I interface to other IMScomponents. DL/I application programs use standard CALL statementswith a parameter list to communicate with IMS. Programs may be writtenin COBOL, PL/I and ASM. Eg: first stmt in IMS program DLITCBL, all

subsequent calls are CBLTDLI.


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IMSComponents (Contd..) &

Features

5. Data Communication Is a set of program modules that allowthe program to communicate with remote terminals. Programscommunicate with terminals through a Standard Interface Languageusing CALL statements with a parameter list.

Primary Products IMS/ESA Transaction ManagerIMS/TM

IMS/ESA Database ManagerIMS/DB

Product Implementations

DC is used to implement the transaction manager DB is used to implement the database manager


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Typical Hierarchical structure

DEALER

MODEL

ORDER STOCK SALES

Parent of Model segment

Child (dependent of dealer

segment parent of order, stock,and sales Segments)

Dependents of Model Segment


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Traversal in IMS database

IMS database traversal generally follows:

Top to bottom

Left to right

Front to back

Illustration follows:


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Traversal in IMS database (Contd..)

Emp - 002Ep - 001

Cp -

SSE

Bd -

22345

67890

Sd - Mar06Sd - Feb06

Sd - Jan06

Ed1

Ec1

Ad1

Sd - Mar06

Sd - Feb06

Sd - Mar05

Sd - Feb05

Bd -

12988

76890

Cp -

SSE

Cp -

SE

Bd -

12345

67890

Sd - Jan05Sd - Jan06

Ed1

Ec1

Ad1


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Explanation of diagram

The diagram shows how the data elements are arranged in IMS. Data

elements are stored in the hierarchical structure or in other way we can say

that some data elements are dependent on other.

Each grouping of data is called as segments.

A segment is the unit of data that DL/I transfers to and from your program.

In previous diagram DEALER, MODEL, ORDER, STOCK and SALES are the

names of segments.


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Concept of Segments

In IMS, segments are defined by the order in which they occur and by their

relationship with other segments.

The segment type at the top level of Hierarchy represents the Root segment.Like in the above case the DEALER represents the root segment.

An occurrence of the root segment plus all the segment occurrences subordinate

to it makes one database record.

All of the segments except the root segment are called dependent segments.

Each dependent segment is also called the child segment.


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Terms in an IMS Database

SEGMENT or SEGMENT TYPE

- A segment is the smallest structure of the database in the sense that IMS

cannot retrieve data in an amount less than a segment

- Within each segment there can be one or more data fields

- A database record can contain a maximum of 255 types of segments and one

hierarchical path can have up to 15 segment types

FIELDS

- Segments can be broken down into smaller increments called fields, which can

be addressed individually by application programs


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Terms in an IMS Database (Contd..)

SEGMENT OCCURANCE

- Segment Occurrence identifies the data that belongs to a particular Segment

Type

PARENT- A segment that has one or more dependant segments beneath it in the

hierarchy.

CHILD

- A segment that is a dependent on another segment above it in the hierarchy.


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Terms in an IMS Database (Contd..)

TWINS

- All occurrences of a particular segment type under a single parentsegment occurrence are called TWINS

DATABASE (IMS)

- A database consists of all root segment occurrences along with theirdependents.

- Is normally shared by multiple applications.

DATABASE RECORD

- A database record has one root segment occurrence along with all theoccurrences of its child segments in hierarchic sequence


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Organization and Access Methods

Organization

The way data is organized. e.g. KSDS,ESDS,RRDS,LDS

Access Method

The process followed to access the data. E.g. VSAM

IMS Access Methods are

Hierarchic sequentially accessed databases

HSAM, SHSAM, HISAM, SHISAM, GSAM

Hierarchic direct databases

HDAM, HIDAM Fast Path databases provide fast access with limited functionality

DEDB, MSDB


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Control Blocks

IMS uses two kinds of control blocks to enable application programs

The database descriptor/definition (DBD) and

Program communication block (PCB).

Database Description (DBD)

A database descriptor (DBD) is a control block that describes thephysical structure of the database. The DBD also defines the appearanceand contents, or fields, that make up each of the segment types in the

database. It describes the way in which it is stored on the DASD and theway it is accessed.


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Control Blocks (Contd..)

Program Communication Block (PCB)

A program communication block (PCB) defines an application

program's view of the database. It describes the logical structure of a

database as a particular program views it. It identifies which pieces of adata a program is allowed to access and the kinds of functions

(operations) it can perform on each collection of data. This is useful

when an application program needs to process only some of the

segments in a database which is a very common need.


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What is DL/I ?

DL/I is Data Language Interpreteris a data management facility that

serves as an interface between an application program and a database.


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DL/I and Application program

DL/I and the Application Program

DATA BASE

OPERATING SYSTEM

DL/I

DBD PSB

APPLICATION PROGRAM

YourAddressSpace orRegion


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How DL/I Relates to your

application program

DATABASE

DATASET

DL/I

APPLICATION

PROGRAM

DL/I DATA BASE

PROCESSING

OPERATING

SYSTEM

ACCESS

METHOD

FILE DATA

SET

STANDARD FILE

PROCESSING

STANDARD

COBOL I/O

STATEMENTS

CALLS TO DL/I

OPERATING

SYSTEM

ACCESS

METHOD

APPLICATION

PROGRAM


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DBD - Data base definition

DBD

A database description/definition (DBD) is a series of macro statements

that define the type of database, all segments and fields, and any logicalrelationships or indexing. DBD macro statements are submitted to the

DBDGEN utility, which generates a DBD control block and stores it in

the IMS.DBDLIB library for use when an application program accesses

the database.

Apart from describing the physical structure and interdependency of

segments in database, it also names the DBD and the access method

that will be used by DL/I for data manipulation.


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Defining DBD

Suppose the ACCENTURE hierarchical structure has been designed. Thename of the segments has been chosen. Now we must tell IMS about thisdatabase. IMS needs to know about all the keys, search fields, andrelationships that are designed as part of the organization database.

The DBD is usually coded by a DBA (Data Base Administrator). It is thensubmitted to the system with JCL that invokes a procedure called DBDGEN.This procedure produces an object module which is in turn passed to thelinkage editor which produces a load module. The load module is stored in alibrary named something like IMSVS.DBDLIB.


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DBD Functions

Defines the physical storage information.

Defines the hierarchical structure.

Define the relationship between the segments.

Defines the segment layouts.

Defines the key field with in the segment. Describe the information necessary to create the database.

Defines any logical relationship.

Defines the secondary index.


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DBD - Data base definitionMacros

DBD Names the database being described and specifies itsorganization.

DATASET Specifies the names of files used to store the data. Defines

each file which comprises the data base. It defines the DDnames and the dataset information.

SEGM Defines the name of the segment type, its position inthe data base and how it is related to other segments.

LCHILD Defines a relationship between two different segmenttypes. This could be an index relationship, a logicalrelationship or a secondary index.

FIELD Defines a field within a segment. It identifies the fieldname, its length in bytes, its starting position, and thetype of data in the field.


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DBD-Data base definition Macros(Contd..)

XDFLD Defines the source fields for a secondary index.

DBDGEN This statement ends the SEGM and FIELD definitions for

the DBD. Marks the end of statements defining the DBD.

END This statement marks the end-of-data to the assembler

process.


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Data Base Descriptor (DBD)(Contd..)

The RULES can be FIRST, LAST AND HERE. This is primarily used forINSERT operations with no key field or has a NON UNIQUE key.

RULES = LASTInsert as the LAST OCCURANCE for the NON

UNIQUE keyRULES =FIRSTInsert as the FIRST OCCURANCE for the NON

UNIQUE key

RULES = HEREInsert at the CURRENT POSITION established in thedatabase for the corresponding NON UNIQUE key

PARENT=(SEGMENTNAME,SNGL)Only pointer

PARENT=(SEGMENTNAME,DBLE)Two pointers DBDGEN process creates the DBD load


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Data types in DBD Macro

The following data types are allowed in a DBDmacro:

C : Character

P : Packed decimal

Z : Zoned decimal

X : Hexadecimal

H : Halfword binary

F : Fullword binary


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Hands On - DBD

Create the structure of a Database from the given DBD in mainframe


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PSBProgram specification block

PSB is the view of an IMS database or the "Program Can Seepart of thedatabase for an application program

Describes the logical structure of one or more data bases to theapplication program

The logical data structure is defined by creating PSB

Defines segment sensitivity for each data base

Defines the processing options for the segments


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PSB - Program specification block(Contd..)

The PSB statements are processed by the PSBGEN and a load

module is produced, much the same as the DBDGEN process.

Within the PSB are one or more control blocks, called PCBs or

program communication blocks. There is a control block for eachdata base that may be accessed. If more than one pointer is

required for processing the data base in the program, then there will

be multiple PCBs for the same data base. If there is a secondary

index associated with the data base, then there is a separate PCB to

specify the secondary index processing option.


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PSB - Program Specification Block

- Macros

PCB Defines the database to be accessed by the applicationprogram. The statement also defines the type of operationsallowed by the application program. Each database requires aseparate PCB statement. PSB generation allows for up to 255

database PCBs.

SENSEG Defines the segment types to which the applicationprogram will be sensitive. A separate SENSEGstatement is required for each segment type. If asegment is defined as sensitive, all the segments in thepath from the root to that segment must also be defined assensitive.


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Macros (Contd..)

SENFLD - Defines the fields in a segment type to which the

application program is sensitive. Can be used only in

association with field-level sensitivity.TheSENFLD

statement must follow the SENSEG statement to which

it is related.

PSBGEN - Identifies the language of the program that will use

the PSB and gives a name to the PSB coded at the

end.


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Macros (Contd..)

PROCOPT-Defines the type of access to a database or segment.

PROCOPTs can be used on the PCB or SENSEGstatements.

Primary PROCOPTcodes are as follows:

G - read only

R - replace, includes G

I - insert

D - delete, includes G


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Macros (Contd..)

A - get and update, includes G, R, I, D

K - used on SENSEG statement; program will have key-only

sensitivity to this segment

L/LS- load database

Secondary PROCOPTcodes are as follows:

E - exclusive use of hierarchy or segments

O - get only, does not lock data when in use

P - must be used if program will issue path call using the D

command code S - sequential (LS is required to load HISAM and HIDAM

databases; GS gets in ascending sequence)


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PSB - Program Specification Block(Contd..)

Illustration of using PROCOPT codes.

PCB TYPE=DB

DBDNAME=INVENORG,

KEYLEN=24,

PROCOPT=GO (G as primary, O as secondary)


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SENSEG NAME=LOCATION,PARENT=0,

PROCOPT=O

SENSEG NAME=PROJECT,PARENT=LOCATION

SENSEG NAME=EMPLOYEE,PARENT=PROJECT,

PROCOPT=A

PSBGEN LANG = COBOL,PSBNAME=ORGAN

END


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TYPE=DB -- required for each database the program can access

TYPE=TP -- required for output message destinations in case of IMS/DC

SENSEG -- required for each segment in the database the application

program can access (up to 30000 SENSEG statements canbe defined for PSB generation)

SENFLD -- required for each field in the segment that an application

program can access (up to 255 SENFLD statements can bedefined for each SENSEG and an overall 10000 SENFLDcan occur in a PSB)

PROCOPT -- required to specify the program's processing options

KEYLEN -- indicates the greatest KEYLEN from all the paths in a DB PSBGEN -- required for each PSB generation

END -- required for each PSB generation


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Hands On - PSB

Create the structure of a PSB from the given DBD in mainframe

How to Run an Application


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How to Run an Application

Program Using DL/I

DL/I Batch initialization module (DFSRRC00).

//STEP1 EXEC PGM=DFSRRC00,REGION=962K,TIME=2,COND=(4,LT),

// PARM=(DLI,PGMNAME,PSBNAME,,,,,,,,,,,N)

Application program and DL/I execute together.

CALL CBLTDLI USING DLI-function

PCB-Mask

Segment-io-area

{ SSA(s) }

COBOL Basics For Processing a


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DL/I database

ENTRY statements

ENTRY 'DLITCBL USING PCB-MASK1

PCB-MASK2PCB-MASK3

The order in which the PCB masks appear in the Entry Statement is

important, the linkage section PCB-Mask's can be in any order.

GOBACK instead of STOP RUN.



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DL/I database (Contd..)

LINKAGE SECTION.

01 PCB-MASK1.

05 PCB-EMPLOYEE-DB.

10 PCB-DBN-DB1 PIC X(08). --> Name of Database

10 PCB-LEV-DB1 PIC X(02). --> Level of last successful

call10 PCB-STC-DB1 PIC X(02). --> Status Code

10 PCB-PRO-DB1 PIC X(04). --> PROCOPT from PSB

10 PCB-RES-DB1 PIC S9(5) COMP. --> Reserved for DL/I

10 PCB-SGN-DB1 PIC X(08). --> Last Segment

Successfully retrieved ina call

10 PCB-LKF-DB1 PIC S9(5) COMP. --> Length of ConcatenatedKey



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DL/I database (Contd..)

10 PCB-NOS-DB1 PIC S9(5) COMP. --> Number of

Segments used to

create the

concatenated key

10 PCB-KFB-DB1 PIC X(26). --> Key Feed Back

Area (to get the

concatenated key)

10 FILLER REDEFINES PCB-KFB-DB1.

15 PCB-KFB-KEY1-SEG1-EMPDB PIC X(06).

15 FILLER PIC X(20). Key


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Some common status codes

SPACESsuccessful retrieval.

GBEnd of database.

GENot found.

II Duplicate segment while insertion.

DAKey field changed.

DJNo get hold call before DLET or REPL.

GKSegment of diff type but at the same hierarchical level.

GAHigher level segment was retrieved during sequential

call.

SSA Segment Search Argument


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SSA - Segment Search Argument

Segment Search Argument

The SSA is used to specify to DL/I the segment and path of the data you

want to access with the DL/I call. In most cases, a separate SSA is used

for each hierarchical level on the path to the required segment. The SSA

may be unqualified or it may be qualified with the key field name andvalue of the segment being accessed.

An example of a typical SSA entry in a COBOL application program. The

KEY-FIELD-VALUE depends on the length of the key field of the

segment being searched.



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(Contd..)

01 SSA1.05 SEGMENT-NAMEPIC X(08).

05 COMMAND-CODES PIC X(03).

05 LEFT-PARENPIC X(01).

05 KEY-FIELD-NAME PIC X(08).

05OPERATORPIC X(02).

05 KEY-FIELD-VALUE PIC X(08).

05 RIGHT-PARENPIC X(01).

CALL CBLTDLI USING CALL-FUNCTION

PCB-DB

IO-AREA

SSA1

SSA2

.

.

.

SSAn.



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SSA Segment Search Argument(Contd..)

An SSA contains the following statements:

SEGMENT NAME - This value tells DL/I which segment to access.

COMMAND CODES - IMS command codes can be used here to modify theDL/I call.

LEFT PAREN (OR SPACE) - If left blank, the SSA will be an unqualified SSA.



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SSA Segment Search Argument(Contd..)

KEY FIELD NAME - The key field, search field, or index field that will be used

in the segment search.

OPERATOR - A relational operator (for example, EQ, GT, LT) can be used.

KEY FIELD VALUE - This is the value of the field that will be processed.

RIGHT PAREN - This statement is used to indicate the end of the SSA.


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Qualified and Unqualified SSAs

Qualified call

A qualified call is the one in which we have SSAs. Qualified call can beeither with Qualified SSA or Unqualified SSA.

Qualified SSA

Has 8 characters segment name followed by ( in the 9thposition of the

SSA defined.

Unqualified SSA

Has 8 characters Segment name followed by space in the 9th position ofthe SSA defined.

Unqualified call

An un-qualified call on the other hand has no SSA.


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DL/I Calls

The purpose of a DL/I call is to instruct DL/I to perform a certain action

involving the data stored in the IMS database.

A DL/I call includes four parts :

CALL FUNCTION - Tells DL/I what needs to be done (for example,

retrieve, update, insert, delete).

PCB - Gives the name of the PCB of the database that will be referenced

by the call.

I/O AREA - Specifies the work area for the requested segment.

SSA - Specifies the segment and path of the data to be accessed.


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DL/I Calls (Contd..)

Format of a DL/I call in a COBOL application program.

CALL CBLTDLI USING CALL-FUNCTION

PCB-DB

IO-AREA

SSA1

SSA2

.

.

.SSAn.


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DL/I Calls (Contd..)

DL/I calls can be subdivided into:

Retrieval calls

Update calls and

Miscellaneous calls

Generally all the DL/I calls are defined in a copybook and copied

into the program. There by reusing the copybook in all IMS

programs. Only calls that are required by a program can be used.


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Retrieval calls

GU(Get Unique) Gets the first segment which matches thequalifiers

GN (Get Next) Gets the next segment in hierarchic order whichmatches the qualifiers in the call

GNP(Get Next Within Parent) Gets the next segment under the current parentwhich matches the qualifiers specified in the call

GHU(Get Hold Unique) Same as GU, but locks the segment forsubsequent update (DLET or REPL)

GHN(Get Hold Next) Same as GN, but locks the segment forsubsequent update (DLET or REPL)

GHNP(GHN Within Parent) Same as GNP, but locks the segment forsubsequent update (DLET or REPL)


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Update calls

ISRT(Insert) To insert a segment in the database

REPL (Replace) To replace an existing segment with new

data (The key to segment can not be

changed, and previous 'GET HOLD'

command must be issued)

DLET (Delete) To delete an existing segment from the

data base (The previous 'GET HOLD'

command must be issued)


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Miscellaneous Calls

CHKP To take a 'check point' or 'commit updates to the databasebefore the program terminates.

XRST To restore the database position after a check point hasbeen taken

PCB To schedule a PSB in an on-line program

TERM To terminate a PSB in an on-line program


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Command Codes

Command Codes in a SSA makes the call powerful since DL/I treats suchSSAs differently from those without the command codes while performingsome special functions.

Command codes save programming and processing time.

Command codes are specified in an SSA following the segment name andan Asterisk *.

* in the ninth position in a SSA indicates that one or more commandcodes follow the * and 10thposition will be reserved for the commandcode.

11thposition will be for the left parenthesis (.

A Blank or Left parenthesis marks the end of the command codes.


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Command Codes(Contd..)

ONE or MORE command codes can be used in any combination usingrelational operators like &.

Command Codes are codes specified in the SSAsthat help to optimizethe performance of IMS programs and leads to Simplified Coding.

Command Codes extend the functionality of DL/I calls.

Multiple DL/I calls can be reduced to a single DL/I call by usingCommand Codes.

If we dont need to use Command Codes while processing we canoverride the existing command code in the program (before the callwhere SSA is used) by passing/using the NULL (-) Command Code.

C C


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The 10 Command Codes available in IMS are :

C Concatenated key in the SSA.

D Retrieve this segment data into the I-O Area (Path call).

F Locate the first segment occurrence that satisfies the SSA.

L Locate the last segment occurrence that satisfies the SSA.

N Do not replace this segment.

Q Locks a segment for your program's exclusive use.

Command Codes (Contd )


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U Specify the current database positions at that level is not allowed tobe changed by the call

P Establish Parentage at this level

V Specify the current database position at that & all levels above arenot allowed to be changed by the call

'NULL Used as the place holder in SSA's so that command codes canbe removed/inserted from SSA's without having to define

separate SSA's in working storage.

Examples for command codes


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Examples for command codes

Command code C can be used to replace multiple SSAs into one single SSA. If we are retrieving just lower level segment occurrences instead of defining multiple

SSAs, with field name, relational op and search value, define the concatenated key forthe segment.

01 Employee-Bankdetl-SSA.

05 Filler pic x(11) value EMPLOYEE*C(.

05 Employee-SSA-empno pic x(06) value spaces.

05 Compdtl-SSA-desg pic x(02) value spaces.05 Bankdtl-SSA-acctno pic x(10) value spaces.

05 Filler pic x value ).

01 Bankdtl-IO-area pic x(21).

.

.

Procedure Division.

Pass the key values to empno, desg and account no. before the call.

Call CBLTDLI Using DLI-GUPCB-Mask

Employee-Bankdetl-SSA

Bankdtl-IO-area

Examples for command codes(Contd )


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(Contd..)

Command code D (path call) can be used to replace multiple IMS CALL statements with a single CALLstatement.

If we need to retrieve all the I/O areas of the path traversed, the calls can be combined together with a I/O areadefinition, that would accommodate all the fields retrieved. IO area should be defined with caution.

01 Employee-SSA.

05 Filler pic x(11) value Employee*D(.

05 Filler pic x(10) value Emplno =.

05 empl-no pic x(06).

05 Filler pic x value ).01 Compdtl-SSA.

.

01 Bankdtl-SSA.

.

01 Path-Call-IO-area.

05 emp-io-area pic x(56).

05 comp-io-area pic x(12).

05 bank-io-area pic x(11).

Procedure Division.

Call CBLTDLI using DLI-GUPcb-mask

path-call-io-area

employee-ssa

compdtl-ssa

bankdtl-ssa

Some examples of IMS retrieval

ll


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calls

GU - Get Unique - Fully Qualified SSA

11000000

10000009

PROJ0002

EMP00002EMP00003

01 LOCATE-QSSA.

05 F PIC X(9) VALUE LOCATION(.

05 F PIC X(08) VALUE LOCATEID.

05 LOCATE-OP PIC X(02) VALUE SPACES.

05 LOCATE-KEY PIC X(08) VALUE ZERO.

05 F PIC X(01) VALUE ).

MOVE 100000009 TO LOCATE-KEY

MOVE EQ TO LOCATE-OP

CALL CBLTDLI USING GU-FUNCTION

ORGAN-PCB-MASK

LOCATE-SEGMENT

LOCATE-QSSAIF LOCATE-PCB-STATUS = bb

CONTINUE

ELSE

PERFORM error-routine.

IMS retrieval calls


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IMS retrieval calls(Contd..)

GU - Multiple Fully Qualified SSAs

10000000

10000009

PROJ0001

PROJ0002

EMP00001

EMP00002EMP00003

MOVE 10000009 TO LOCATE-KEY


MOVE PROJ0002 TO PROJECT-KEY

MOVE EQ TO PROJECT-OP


PARTS-PCB-MASK

SUPPLIER-SEGMENT

LOCATE-QSSA

PROJECT-QSSA

IF LOCATE-PCB-STATUS = bb

CONTINUEELSE



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IMS retrieval calls (C td )


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IMS retrieval calls (Contd..)

GUMULTIPLE - Unqualified SSA

11000000

10001009

10000001

PROJ0001

PROJ0002

EMP00001

EMP00002

EMP00003

01 LOCATION-USSA. PIC X(9) VALUE LOCATION .

01 PROJECT-USSA PIC X(9) VALUE PROJECT .

01 EMPLOYEE-USSA PIC X(9) VALUE EMPLOYEE .

05 F PIC X(9) VALUE LOCATION .


ORGAN-PCB-MASK

EMPLOYEE-SEGMENT

LOCATION-USSA

PROJECT-USSA

EMPLOYEE-USSA.


CONTINUE

ELSE




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GUMISSING - SSAS

11000000

10001009

10000001

PROJ0001

PROJ0002

EMP00001

EMP00002

EMP00003

01 LOCATE-QSSA.



ORGAN-PCB-MASK

PROJECT-SEGMENT

PROJECT-USSA

EMPLOYEE-USSA.

IF ORGAN-PCB-STATUS = bb

CONTINUE

ELSE


IMS retrieval calls (Contd )


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GUNO - SSAS

11000000

10001009

PROJ0001

PROJ0002

EMP00001

EMP00002

EMP00003


ORGAN-PCB-MASK

LOCATE-SEGMENT

IF ORGAN-PCB-STATUS = bb

CONTINUE

ELSE




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GN - Fully Qualified SSA

11000000

10000009

PROJ0001

PROJ0002

EMP00001

EMP00002EMP00003

01 LOCATE-QSSA.

05 F PIC X(9) VALUE LOCATION(.

05 F PIC X(08) VALUE LOCATEID.

05 LOCATE-OP PIC X(02) VALUE ZERO.

05 LOCATE-KEY PIC X(08) VALUE ZERO.

05 F PIC X(01) VALUE ).MOVE 110000000 TO LOCATE-KEY


CALL CBLTDLI USING GN-FUNCTION

ORGAN-PCB-MASK

LOCATE-SEGMENT

LOCATE-QSSA


CONTINUE

ELSE




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GN - Unqualified SSA

11000000

10001009

PROJ0001

PROJ0002

EMP00001

EMP00002

EMP00003

01 LOCATE-QSSA.

05 F PIC X(9) VALUE EMPLOYEE .


ORGAN-PCB-MASK

LOCATE-SEGMENT

EMPLOYEE-USSA.


CONTINUE

ELSE




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11000000

10001009

10000001

PROJ0001

PROJ0002

EMP00001

EMP00002

EMP00003


ORGAN-PCB-MASK

EMPLOYEE-SEGMENT

LOCATION-QSSA

PROJECT-QSSA

EMPLOYEE-USSA.


CONTINUE

ELSE


GNMULTIPLEUnqualified SSAS



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11000000

10001009

10000001

PROJ0001

PROJ0002

EMP00001

EMP00002

EMP00003


ORGAN-PCB-MASK

GENERAL-IO-AREA .

IF LOCATE-PCB-STATUS = bb OR GA OR GK

CONTINUE

ELSE


GN-Combination of SSA types



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11000000

10001009

10000001

PROJ0001

PROJ0002

EMP00001

EMP00002

EMP00003

01 LOCATION-USSA. PIC X(9) VALUE LOCATION .

01 PROJECT-USSA PIC X(9) VALUE PROJECT .

01 EMPLOYEE-USSA PIC X(9) VALUE EMPLOYEE .



ORGAN-PCB-MASK

EMPLOYEE-SEGMENT

LOCATION-USSA

PROJECT-USSA

EMPLOYEE-USSA.


CONTINUE

ELSE


GN - No SSAS



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GNPGET NEXT WITH IN PARENT

11000000

10001009

10000001

PROJ0001

PROJ0002

EMP00001

EMP00002

EMP00003


ORGAN-PCB-MASK

LOCATION-SEGMENT

LOCATIONI-QSSA

IF ORGAN-PCB-STATUS = BB

PERFORM 1500-GNP-PROJECT

UNTIL ORGAN-PCB-STATUS = GE

ELSE PERFORM ERROR-ROUTINE

1500-GNP-PROJECT.

CALL CBLTDLI USING GNP-FUNCTION

ORGAN-PCB-MASK

SUPPLIER-SEGMENT

PROJECT-USSA

ISRT Calls


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ISRT Calls

Inserts a new segment occurrence. Before issuing the call, you must

populate the I/O area for the new segment. The I/O area must contain the

same fields in the same order, length, and data types that exist on the

segment being inserted.

ISRT Calls are used to add segments to a DL/I database either during theupdate processing of new segments or during the load operation.

ISRT calls can use qualified or unqualified SSA s, E.g. Of ISRT Call usingan unqualified EC SSA, make sure of the pointer before unqualified call.

ISRT Calls (C td )


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ISRT Calls(Contd..)

DL/I will try to execute this call by inserting the EC occurrence in the Database basedon the current position in the database

CALL 'CBLTDLI' USING CN-ISRT

PCB-MASK1

WK-OUTPUT-REC

WS-UNQUAL-EC-SSA

E.g. Of ISRT Call using a qualified call

CALL 'CBLTDLI'USING CN-ISRT

PCB-MASK1

WK-OUTPUT-RECWS-QUAL-EMP-SSA

WS-QUAL-CP-SSA

WS-UNQUAL-BD-SSA

ISRT Calls (Contd )


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ISRT Calls(Contd..)

DL/I will try to execute this call by inserting the BD occurrence in theDatabase based on the position obtained from the QUAL-EMP segmentoccurrence and the QUAL-CP segment occurrence.

DL/I returns status code GE if the segment occurrence mentioned usingthe qualified SSA s is not found.

When the lower level segment types in a database have non uniquesequence fields or dont have any sequence fields then the ISRT worksbased on RULES specified in the DBD.

RULES = FIRST, the new segment occurrence is inserted before allexisting twins

RULES = LAST, the new segment occurrence is inserted after all existingtwins

ISRT Calls (C td )


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ISRT Calls(Contd..)

RULES = HERE, the new segment occurrence is inserted at the currentposition in the database

The RULES mentioned in the DBD can be overridden by CommandCode

RULES = FIRST can be overridden by coding Command Code L inSSA

However RULES = LAST, CANNOT be overridden by coding CommandCode F

The D Command Code can be specified to insert more than onesegment occurrence types along a path

ISRT Calls (Contd )


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ISRT Calls(Contd..)

When D Command Code is being used for insert, the PROCOPT=P shouldbe specified in the PSB.

For Load operation, all segments must be inserted in hierarchical sequence.Also the PSB must have PROCOPT = L or LS.

The Status Code GE during ISRT calls happen when the segment occurrencebeing inserted with Qualified SSA s is not present in the database.


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ISRT Calls (INSERT MODE)

Status Codes


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Status Codes

The following are some status codes encountered while issuing a ISRTcall to insert a segment into an already loaded database:

IIThe segment already exists in the database. A duplicate key value

is being inserted into.

IXEncountered an Insert Rule Violation. Program tried to insert a

segment into the wrong place. For e.g. A stock segment is being

inserted under the Dealer segment, when it is in fact dependant

upon the Model segment.

ISRT Calls (LOAD MODE)Status

Codes


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Codes

The following are some status codes encountered while issuing a ISRTcall to load segments into an empty database:

LBWhen you try to load the same segment twice i.e. segment already

exists

LCThe segments being loaded are not in their Hierarchical sequencei.e. key values out of sequence

LDNo Parent for the segments being loaded. You cannot load a

dependant segment until its parent has been loaded

LESegment types out of sequence. For e.g. If you tried to load a stock

segment before a model segment

REPL Calls


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Replaces current data in a selected segment with new data from the I/O area.

It must be preceded by a GHU, GHN, or GHNP call.

A REPL generally does not use an SSA. The segments key fields cannot be

changed.

There are two restrictions for REPL Calls

Cannot ch ange the length of the Segment

Cannot c hange the value of the Sequence Field

Never Code a qualified SSA on a REPL Call. Replace processing can be done

with Path Calls.

REPL Calls(Contd..)


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( )

For Replace operation with Path Calls, we can negate replacement of certainintermediate segment occurrences by giving Command Code N

E.g. Of REPL Call

CALL 'CBLTDLI' USING CN-GHUPCB-MASK1

WK-REC

WS-QUAL-EMP-SSA

WS-QUAL-SAL-SSA

WS-QUAL-TAX-SSA

Change some values obtained in WK-REC


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REPL Calls(Contd..)


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The Status code AJ happens when we try to use Qualified SSA on a

REPL Call

The Status Code DJ happens when a GHU or GHN call doesnt precede

the REPL Call

The Status Code DA happens when the program tries to make change

to the Segment Key field before giving REPL call

REPL Calls Status Codes


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REPL Calls Status Codes

The following are some status codes encountered while issuing a REPLcall :

DJReplace call issued without an immediately preceding GETHOLD

call

DAProgram has changed the segments KEY FIELD

RXEncountered a Replace Rule Violation

AJUsed a qualified SSA

DLET Calls


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Deletes the segment previously retrieved and all of its dependents, even if

the application is not defined as sensitive to them. It must be preceded by

a GHU, GHN, or GHNP call (see GET HOLD Calls). Deletes generally do

not use SSAs.

Works similar to a REPL call, a Get Hold Call should be given first followedby a DLET call.

Never code a qualified SSA with DLET call.

Unqualified SSA s can be coded in a DLET call when we are using PathCalls (Command Code D, since the pointer position is known)

DLET Calls(Contd..)


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A DLET Path Call will delete the entire path.

The scope of a Path Delete can however be limited by supplying oneunqualified SSA without a command code, such calls should be avoidedunless sure of the pointer position.

The Status code AJ happens when we try to use Qualified SSA on a DLETCall.

The Status Code DJ happens when a GHU or GHN call doesnt precede theDLET Call.

The Status Code DA happens when the program tries to make change to theSegment Key field before giving DLET call.

DLET CallStatus Codes


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The following are some status codes encountered while issuing a DLETcall :

DJDelete call issued without an immediately preceding GETHOLD

call

DAProgram has changed the segments KEY FIELD

DXEncountered a Delete Rule Violation

AJUsed a qualified SSA

Some more DL/I Status codes


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AB The call did not specify a segment IO area AC SSA with a hierarchical error

AH Call requires at least one SSA

AJ Call specifies an Invalid SSA

AI Error encountered when trying to open the database

dataset. An error in the JCL DD statement

AK The field named in a qualified SSA is not correct

AT The IO area specified in the call is too large but the

programs PSB may be incorrect

AO Call caused an operation resulting in a physical IO error

System ServiceDL/I Calls


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The four important DL/I calls that perform various system servicefunctions are : 1) CHKP 2)XRST 3)ROLL 4)ROLB

CHECKPOINT (CHKP) Call A point in the execution of program when the changes made to the

database are considered complete and accurate.

Checkpoint (CHKP) call is used for recovery purposes, in the IMSprogramming environment it is the method used to ensure data integrity.

Once check pointed, the changes made are not reversible.

CHKP call causes all the database changes made since the lastcheckpoint to be permanently committed to the physical database therebymaking Backout impossible.

A CHKP call causes the database position for a PCB to be reset, apartfrom releasing all the locks held by the program.

System ServiceDL/I Calls

(Contd..)


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( )

In addition, the CHKP call

Enables you to save as many as seven data areas in your program,which are restored when your program is restarted

In case of ABENDs, IMS will control the process of backing outdatabase updates up to the last checkpoint.

Works with the Extended Restart (XRST) call to restart your program if itterminates abnormally


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Exercises (Contd..)


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DOCTORDOC_NAME PIC X(20)

DOC_ADDR PIC X(50)

DOC_PHONE PIC X(10)

DOC_SPL PIC X(15)

Assume the following data is available in the database:

WARD Segment:

101, 20, 25, F

102, 10, 22, G

103, 30, 45, M

Exercises (Contd..)


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PATIENT Segment:1001, PAUL, 101/B OAK WOOD NY, 41278906

1231, SIMPSON, 123/C JOHN STREET NJ, 4177231

1231, CATHY, 77-Y WINSTON ROAD ATLANTA, 7634211

1001, PAUL, 101/B OAK WOOD NY, 41278906

DOCTORSegment:

SAMUEL, 11-9 KENNEDY ST CAL, 890076, ORTHO

RANDY, 15/A PERKIN HALL IN, 77886611, DENTIST


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Exercises (Contd..)


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4. Write aDLET call to delete theWARDrecord.

102, 10, 22, G

5. Write anISRT call to insert theDOCTOR record.

CHRISTY, 78/L TOM ST OHIO, 892357, OPTHALMOLOGY

Case StudyHR Application


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