IMS Database Processing

8/22/2019 IMS Database Processing

1/34

IMS-DB

Information Management System

DB Concepts & Programming

HOME
http://www.geocities.com/srcsinchttp://www.geocities.com/srcsinc


2/34

HOME

Files Vs Databases

Networked,Hierarchical & Relational structure

Access types - HSAM, HISAM,HDAM,HIDAM,VSAM

IMS DB - an Hierarchical Structure

Database Definitions - DBD

Program Specification Block ,Program Control Block

DL/I Calls - Data Retrieval and Manipulation

DL/I Functions

Qualified/ Unqualified Calls, SSAs, Command Codes

DL/I Status codes

Basic Topics

HOME
http://www.geocities.com/srcsinchttp://www.geocities.com/srcsinchttp://www.geocities.com/srcsinchttp://www.geocities.com/srcsinc


3/34

HOME

Advanced Topics

Data Sensitivity - Segment Level & Field level

Checkpoint & Restart

IMS DB in CICS Environment Secondary Indexing

Difference between MPP, BMP, DLI

Using HFCTDLI

HOME
http://www.geocities.com/srcsinchttp://www.geocities.com/srcsinchttp://www.geocities.com/srcsinchttp://www.geocities.com/srcsinc


4/34

HOME

File Vs Databases

Data more redundant Redundancy avoided

Duplicate data Minimise Duplicates

Data insecure Security provided

No control over data Field level sensitivity

Threat to Integrity Consistency of data

Lack of inbuilt Data Logging,

recovery features Commits & Rollbacks Lack of data Locks Automatic locks


5/34

HOME

Database Structures

Network Structures (e.g IDMS)

Many to Many relationships

Complex structure using Pointers

Best for Keeping storage

Hierarchical Structures (e.g IMS DB)

One to Many Relationships

Inverted Tree like Structure

Best for storing parent and child type entities

Relational Structures (e.g DB2)

One to Many, Many to One

Best for ease of data retrieval


6/34

HOME

Access Types

HSAM/SHSAM (Simple /Hierarchic sequential Access Method)

The segments that make up the database record are related to one another by

their physical locations (SHSAM has only root occurrences)

HISAM/SHISAM(Simple / Hierarchic Indexed Sequential Access Method)

The data is stored with hierarchic sequential organization along with an index

for random processing (SHISAM has only index of root occurrences)

HDAM(Hierarchic Direct Access Method)The segment occurrences include prefixes that contain the direct address

pointers to related segment - stores root segment occurrences

HIDAM(Hierarchic Indexed Direct Access Method)

Similar to HDAM but stores an index of the root segment occurrences


7/34

HOME

IMS DB Hierarchical Structure

SRCSInformationDatabase

Stratergic BusinessUnits info

Project Info

Client Info Employee data

Employee SalaryDetails

Projects

Clients

Salary

Employ

SRCSunits


8/34

HOMEBasic IMS Terminologies

SRCS Units

21

3

Clients Employ

Projects Salary

Segment

Occurrence

Root Segment

Parent SegmentChild Segment

Segment Level

Path

Database Record

TwinsSequential Processing

Random Processing

SRCS

Information

Database

Client Info

Project Info


9/34

HOME

Definitions

Segment

- Unit of Information handled in IMS

- Unit of data transferred from DL/I in an IO operation

- Consists of fields, key fields & Search fields

Occurrence

- Specific segment of a particular type of segment

- Contains actual user data

Root Segment

- Top of the hierarchy

- All other segments are derived from the root

Parent Segment

- Segment that has dependent segments


10/34

HOMEDefinitions (contd)

Child Segment- A dependent segment

Segment Level

- Depth of an IMS structure

- Root is at Level 0, max 15 levels, max 255 segments Path

- Series of segments from Root to the child

Database record

- Each occurrence of the Segment Plus alloccurrence of the subordinate segments

Twins

- Segment occurrences of same type with same parent

segment occurrence


11/34

HOMEIMS Control Blocks

IMS

PGM1IMS

PGM2

DL/I

CONTROL

UNIT

DBD1 DBD2 DBD3

PCB for DB1PCB for DB2

PCB for DB3

PSB

DBDs

IMS DBsDB1 DB2 DB3


12/34

HOME

DBD : Names the database and identifies the access method

DBD Name = SRCS, ACCESS=(HIDAM,VSAM)

DATASET : Specifies DD Name used in the JCL and other parameters

DATASET DD1=DDSAT,DEVICE=3380,SIZE=(4096),FRSPC=(0,15)

SEGM : Names the segment. Identifies the parent and establishes the length

SEGM Name =SRU,PARENT=0,BYTES=40

LCHILD : Names the logical segment used in secondary Indexing and Logical

database

LCHILD NAME=(SRUNAME,SRCS1),PTR=INDX

FIELD : Defines fields. And identifies search &key fields by SEQ parameter

FIELD NAME=(SRUCODE,SEQ,U)BYTES=3,START=1,TYPE=C

DBDGEN: Indicates the end of the DBDGEN process

DBDGEN

COMMENT: * IN 3rd COLUMN for writing user comments

DBD : Database Description, describes physical Database

DBDGEN : DBDGEN Utility, Describes the physical structure of

the Database and creates DBD


13/34

HOME

Sample DBD Listing for SRCS Info Database

DBD NAME=SRCS,ACCESS=(HIDAM,VSAM)

DSG1 DATASET DD1=DDSAT,DEVICE=3380,SIZE=4096,FRSPC=0,15)

SEGM NAME=SRU,PARENT=0,BYTES=40

FIELD NAME=(SRUCODE,SEQ,U),BYTES=3,START=1,TYPE=P

FIELD NAME=SRUNAME,BYTES=5,START=4,TYPE=CFIELD NAME=SRULOC,BYTES=12,START=9,TYPE=C

FIELD NAME=SRUHEAD,BYTES=20,START=21,TYPE=C

SEGM NAME=CLIENT,PARENT=SRU,BYTES=45

FIELD NAME=(CLTID,SEQ,U),BYTES=4,START=1,TYPE=P

FIELD NAME=CLTNAME,BYTES=10,START=5,TYPE=C

FIELD NAME=CLTLOC,BYTES=11,START=15,TYPE=C

FIELD NAME=CLTHEAD,BYTES=20,START=26,TYPE=C


14/34

HOMESEGM NAME=PROJECT,PARENT=CLIENT,BYTES=35

FIELD NAME=(PRJID,SEQ,U),BYTES=4,START=1,TYPE=P

FIELD NAME=PRJNAME,BYTES=5,START=5,TYPE=C

FIELD NAME=PRJTMSIZE,BYTES=4,START=10,TYPE=CFIELD NAME=PRJHEAD,BYTES=22,START=14,TYPE=C

SEGM NAME=EMPLY,PARENT=SRU,BYTES=40

FIELD NAME=(EMPID,SEQ,U),BYTES=5,START=1,TYPE=P

FIELD NAME=EMPNAME,BYTES=10,START=6,TYPE=C

FIELD NAME=EMPPROJ,BYTES=5,START=16,TYPE=CFIELD NAME=EMPADDR,BYTES=20,START=21,TYPE=C

SEGM NAME=SALARY,PARENT=EMPLY,BYTES=35

FIELD NAME=(SALEMPID,SEQ,U),BYTES=5,START=1,TYPE=P

FIELD NAME=SALBASIC,BYTES=10,START=6,TYPE=C

FIELD NAME=SALHRA,BYTES=5,START=16,TYPE=CFIELD NAME=SALDA,BYTES=5,START=21,TYPE=C

DBDGEN

FINISH

END


15/34

HOMEPSBProgram Specification Block,describes Logical structure of the Database that a

program will use.It contains one or more PCBs (Program Communication Block).

PCB describes one Database.

PSBGEN

PSBGEN Produces a load module stored in the PSBLIB library and creates PSB

Major Macros UsedPCB : Describes type (DB or DC), name of the DBD, Key length(length of

the longest concatenated key the program can process) andprocessing Option (Defines how the segment may be accessed)

PCB TYPE=DB,DBDNAME=SRCS,KEYLEN=20,PROCOPT=LS

SENSEG : Define the name of the segments in the Database your program

needs access to

SENSEG NAME=CLIENT,PARENT=SRUSENFLD : Subordinate to the SENSEG macro, only fields that are defined by

the SENFLD macro can be accessed from the I/O Area.

SENFLD NAME=PROJECT,PARENT=CLIENT

PSBGEN PSBNAME=MYPSB,LANG=COBOL

END


16/34

HOMESAMPLE PSB FOR SRCS INFO DB PROJECT REFERENCE PROGRAM


SENSEG NAME=SRU,PARENT=0

SENSEG NAME=CLIENT,PARENT=SRUSENSEG NAME=PROJECT,PARENT=CLIENT


END

SAMPLE PSB FOR SRCS INFO DB PROJECT REFERENCE PROGRAM


SENSEG NAME=SRU,PARENT=0

SENSEG NAME=CLIENT,PARENT=SRU

SENSEG NAME=PROJECT,PARENT=CLIENT

SENSEG NAME=EMPLY,PARENT=SRU

SENSEG NAME=SALARY,PARENT=EMPLY


END
http://www.geocities.com/srcsinchttp://www.geocities.com/srcsinchttp://www.geocities.com/srcsinc


17/34

HOMEDL/I INTERFACE

DL/I passes control to your program

Uses ENRTY and CALL statement to code DL/I call in the Procedure Division

ENTRY DLITCBL USING PCB-name1

PCB-name2

This DL/I tells entry of the program for Batch program & MPP program

CALL CBLTDLI USING DLI-FUNCTION

PCB-mask

Segment-io-area

[segment search arguments (s)]

This call is the name of the interface module that link edited with your

programs object module.


18/34

HOMECALL PARAMETERS

CALL CBLDTLI USING DLI-FUNCTION

PCB-maskSegment-io-area

[segment search argument (s) ]

If we use PL/I language then CBLTDLI will be PLITDLI

Parameter Function

DL/I -Function A four byte code that tells DL/I what kind of call to make

PCB-mask Arguments tells DL/I which PCB to use for the call

IO-Area Tells DL/I where to put the segment

SSA Gives DL/I additional criteria to use in finding a particularSegment, Can be upto 15 SSAs


19/34

HOMEDL/I FUNCTIONS

GU - Get UniqueGN - Get Next

GNP - Get Next within Parent

GHU - Get Hold Unique

GHN - Get Hold Next

GHNP - Get Hold Next within ParentISRT - To Insert

REPL - To replace

DLET - To Delete

CHKP - To take a Checkpoint at a particular point

XRST - To Restart from Particular point previous Checkpoint

INIT - To Initialize

SYNC - To commit


20/34

HOMEPCB MASK

Define in linkage Section and establishes correspondence between linkage Section

PSB-mask and PSBs with in your program.

SAMPLE PCB-MASK LAYOUT

VARIABLE DESCRIPTION

01 SRCS-PCB-MASK.03 SR-DBD-NAME PIC X(8).Name of the Database being processed

03 SR-SEG-LEVEL PIC XX. Specifies current segment level in the DB

03 SR-STATUS-CODE PIC XX. Contains data yr program will evaluate after call

03 SR-PROC-OPT PIC X(4). Type of processing the program authorized to do

03 SR-SEG-NAME PIC X(8). Stores name of the segment just proceeded03 SR-KEY-LENGTH PIC S9(5). Length of the concatenated key

03 SR-NUM-SENSEGS PIC S9(5).No of SENSEG macros subordinate to the PCB

03 SR-KEY-VALUE PIC X(20). Key value retrieved


21/34

HOMEI-O AREA LAYOUT FOR SEGMENTS

SRUCODE SRUNAMESRULOC SRUHEAD

01 SRU-AREA.

03 SRU-CODE PIC X(3).

03 SRU-NAME PIC X(5).

03 SRU-LOC PIC X(12)

03 SRU-HEAD PIC X(20).

CLTID CLTNAME CLTLOC CLT-HEAD01 CLIENT-AREA.

03 CLT-CLTID PIC X(4).

03 CLT-CLTNAME PIC X(10).

03 CLT-CLTLOC PIC X(11)

03 CLT-CLTHEAD PIC X(20).

PROJID PRJNAME TMSIZE PRJADDR

01 PRJ-AREA.

03 PRJ-PROJID PIC X(4).

03 PRJ-PRJNAME PIC X(5).

03 PRJ-TMSIZE PIC X(4)03 PRJ-HEAD PIC X(20).

EMPID EMPNAME EMPPROJ EMPADR

01 EMP-AREA.

03 EMP-ID PIC X(5).

03 EMP-NAME PIC X(10).

03 EMP-PROJ PIC X(5)

03 EMP-ADR PIC X(20).

01 SAL-AREA.

03 SAL-EMPID PIC X(5).

03 SAL-BASIC PIC X(10).

03 SAL-HRA PIC X(5).

03 SAL-DA PIC X(5).

EMPID BASIC HRA DA


22/34

HOMESEGMENT SEARCH ARGUMENT

Identifies Segment Occurrence You want to access

You may have to code several SSAs in a single DL/I CALL

There are two types of SSAs Unqualified SSA & Qualified SSA

UNQUALIFIED QUALIFIED

Search for a Specific Segment type Searches for a specific occurrence of a

specific segment type

Access the database Sequentially Access the database Randomly

Identify by segment name and space Identify by segment name and Seg-key

Example01 UNSRU-SSA. 01 QUALKBU-SSA.

03 SRU-UNSSA-NM PIC X(8) Value SRU . 03 SEG-NAME PIC X(8)VALUE SRU .

03 FILLER PIC X Value Space. 03 COM-CODE PIC X(2) VALUE *

-.

03 BEGIN-QUAL PIC X VALUE (.

03 KEY-NAME PIC X(8) VALUE SRUKEY.

03 REL-OPR PIC X(2) VALUE = .

03 KEY-VALUE PIC X(20).

03 END-QUAL PIC X VALUE ).


23/34

HOMECOMMAND CODES

Command Code Description

D Retrieve Path

F Access First Segment occurrence

L Access Last Segment occurrence

U Maintain current position at this level

V Maintain current position at this level and higher levels

Q Enqueue Segment

N Do Not replace this Segment

C Use a Concatenated Key

P Establish Percentage at this level

- Null command code / ignore


24/34

HOMEData Sensitivity

DBAAt a PSB level for SEGMENTS PROCOPT

PCB TYPE=DB,DBDNAME-SRCS,,KEYLEN=11,PROCOPTSENSEG NAME =SRU,PARENT=0

SENSEG NAME =CLIENT,PARENT=SRU

Processing Options : G, I, R, D, A, P, O, N, T, E, L, GS, LS, H

At a PSB level for fields

Done by DBA by use of SENFLD macro , specifying those fields

that can be changed.

ProgrammerAt PROGRAM Level- Qualified SSA call with Command code N (No Replacement)


25/34

HOMECheckpointing & Restart

A point in the program where the database changes the program made are

Considered complete and accurate -written to a DL/I log

Used for Recovery Process

Are of two types - Basic Checkpointing and Symbolic Checkpointing Basic Checkpointing

CALL CBLTDLI USING DLI-CHKP,

I-O-PCB-MASK,

CHECKPOINT-ID.

Symbolic Checkpointing

Stores program data along with checkpoint records and retrieves that data

when program restarts after failure.

For extended Restart , an XRST call to be issued with the same fields as in

CHKP call. It allows DL/I to retrieve the value in checkpoint record and

restores the specified fields.


26/34

HOMEExplosive Mix - IMS DB with CICS

Scheduling Call

CICS Region / Partition

User Task

User Interface Block

(UIB)

Program Communication

Block

(PCB)

A DL/I task must establish addressability to UIB and one or more PCB


27/34

HOMEIMS & CICS Continued

CALL CBLTDLI USING FUNC-INIT

PSB-NAME

ADDRESS OF DLIUIB

SET ADDRESS OF PCB-ADDR-LIST TO UIBPCBAL

SET ADDRESS OF PCB-1 TO PCB-1-ADR

SET ADDRESS OF PCB-2 TO PCB-2-ADR

...

User Interface Block

Address of PCB List

Address of PCB 1

Address of PCB 2PCB Address list

PCB1

PCB2


28/34

HOMESecondary Indexing

Employee Index Database

EMP..SegAddr

Employee ID

Index Pointer SegmentSRU

CLIENTS EMPLOYEE

PROJECTS

Index Source Segment

Index Target

Segment

Same index Source segment and index target segment


29/34

HOMESecondary Indexing Continued

Employee Index Database

SRU..SegAddr

Employee ID

Index Pointer SegmentSRU

EMPLOYEE

Index Source Segment

Index Target

Segment

Different index Source segment and index target segment

CLIENTS

PROJECTS


30/34


Alternate sequencing is provided by storing pointers to Segments of the indexed

Database in a separate secondary index data base

Secondary index data base has only one segment type - the Index pointer segment

which in turn contains a prefix element and a data element

Prefix element points to the index target segment

Secondary indexing is useful for accessing segments were both

Index source segment and index target segment are same

Index source segment and index target segment are different

Two DBDGENS are required as a secondary database involves two database: one

for indexed database , the other for the secondary index database


31/34


DBDGEN - The Secondary Index code for SRCS DB

DBD NAME=SRCS,ACCESS=(HIDAM,VSAM)

DSG1 DATASET DD1=DDSAT,DEVICE=3380,SIZE=4096,FRSPC=0,15)

SEGM NAME=SRU,PARENT=0,BYTES=40

FIELD NAME=(SRUCD,SEQ,U),BYTES=2,START=1,TYPE=P

SEGM NAME=EMPLY,PARENT=SRU,BYTES=80

LCHILD NAME= (MYPNTR,MYDBD),POINTER=INDX

FIELD NAME=(EMPID,SEQ,U),BYTES=5,START=1,TYPE=P

XDFLD NAME=MYINDX,SRCH=EMPID

FIELD NAME=EMPNAME,BYTES=25,START=6,TYPE=C

FIELD NAME=EMPPROJ,BYTES=15,START=31,TYPE=C

FIELD NAME=EMPADDR,BYTES=35,START=46,TYPE=C

.


32/34


DBDGEN - The Secondary Index code for Secondary Index DB

DBD NAME=MYIDBD,ACCESS=(INDEX)DSG1 DATASET DD1=DDKAY,DEVICE=3380,SIZE=4096,FRSPC=0,15)

SEGM NAME=MYPNTR,PARENT=0,BYTES=6

LCHI LD NAME= (EMPID,SRCS), INDX=MYINDX

FIELD NAME=(MYEMPID,SEQ,U),BYTES=6,START=1,TYPE=C

DBDGEN

FINISH

END

PSB Requirements for Secondary Indexing.

PCB TYPE=DB,DBDNAME=SRCS,KEYLEN=10,PROCOPT=LS,

PROCSEQ=MYIDBDSENSEG NAME=EMPLY

SENSEG NAME=SRU,PARENT=EMPLY

PSBGEN PSBNAME=MYSBX,LANG=COBOL

END


33/34

HOMEDifference Between MPP , BMP & DLI

MPP (Message Processing Program)

For Online programs( IMSDC) only.

PSB used by a MPP program cannot be used by another programs simultaneously.Cannot run on Individual partitions.

BMP (Batch message processing)

For batch programs only

PSB used by a BMP program cannot be used by another programs simultaneously.All partitions specified in PSB will be allocated whether used by program or not.

Cannot run on Individual partitions.

DL/I

It can be used as Interface between MPP and Database OR BMP and Database

For batch DL/I job it can access database directly

PSB of DL/I job can be used by another jobs simultaneously

It can run on Individual partitions.


34/34

HOME

IMS Database Processing

Documents

Transcript of IMS Database Processing