IMSDB Important Tips

IMS-DB DL/I It is a user interface language used to access IMS Databases. DBD It describes the physical nature of the database. PRIN...

IMS-DB

DL/I

It is a user interface language used to access IMS Databases.

DBD

It describes the physical nature of the database.

PRINT NOGEN

DBD NAME=DBDNAME, ACCESS= (HISAM, ISAM)

DATASET DD1=PRIME, OVFLW= OVERFLOW, DEVICE= 3390

SEGM NAME=HOSPITAL, PARENT=0, BYTES=80

FIELD NAME= (HOSPID, SEQ, U), BYTES=10, START=1, TYPE=C

SEGM NAME=WARD, PARENT=HOSPITAL, BYTES=80

…

DBDGEN

FINISH

END

PSB

It describes the logical nature of the database.

PCB (Program Communication Block)

Each PCB in the PSB defines one logical data structure.

PRINT NOGEN

PCB TYPE=DB, NAME=DBDNAME

SENSEG NAME=HOSPITAL, PARENT=0, PROCOPT=K

SENSEG NAME=WARD, PARENT=HOSPITAL, PROCOPT=G

SENFLD NAME=WARDNO, START=1

…

PSBGEN LANG=PLI, PSBNAME=PSBNAME

END

ENTRY STATEMENT

Assigns a standard IMS name to the entry point of the program

PLITDLI / DLITPLI – gives the entry point of an IMS PLI program

CBLTDLI / DLITCBL – gives the entry point of an IMS COBOL program

CALL

CALL statement parameter list and the data items in the parameter list makes the

DL/I Interface language

DL/I Functions

GU, GN, GNP, GHU, GHN, GHNP, ISRT, DLET, REPL

PCB-MASK

DCL 01 PCB-MASK

02 DBD-NAME PIC X (8),

02 SEG-LEVEL PIC X (2),

02 STATUS-CODE PIC X (2),

02 PROC-OPTIONS PIC X (4),

02 JCB-ADDR PIC X (4),

02 SEG-NAME PIC X (8),

02 KEY-LENGTH PIC S9 (5),

02 NUM-OF-SEG PIC S9 (5),

02 KEY-FEED

SSA (Segment Search Arguments)

It is used to identify a particular segment type or occurrence

Up to 15 SSA can be specified in a CALL

Qualified SSA

SSA indicating the segment type and a specific occurrence

In the 9^th position, it’s having the left open parenthesis

Unqualified SSA

SSA indicating the segment type and not an occurrence

In the 9^th position, it’s having a space

Load Mode Status Code:

LB – Segment already Exist

LC – Key out of Sequence

LD – No parent for segment being loaded

LE – Segment type out of sequence

Insert Mode Status code:

II – Segment already Exist

IX – Insert Rule violation

DBD Insert Rules:

- Rules in PCB is used to specify in where the segment occurrence is inserted if the

Segment type doesn’t have key field

• Three options are FIRST,LAST AND HERE. Default is last if rules not coded.

Ex:

SEGM NAME=DOCTOR, PARENT=WARD, BYTES=80, RULES= (, HERE)

REPLACE RULES:

No other call referencing the same PCB are allowed between GET HOLD and REPLACE

CALL

DELETE RULES

A CALL does not include SSA’s when issuing DELETE or REPLACE

Only exception is using D Command code is to replace all segments in a path

DELETE MODE STATUS CODE

DJ – No previous successful GET HOLD call

DA – Key field modified

DX – Delete rule violation

RX – Replace rule violation

AJ – a qualified SSA is given in REPL call

COMMAND CODES

Allows the program to request a number of DLI functions for speed processing and

Time saving

C – Concatenation

D – Gives all segment hierarchy occurrences in the CALL statement

F – Retrieve first occurrence

L – Retrieve last occurrence

N – Doesn’t allow updating

P – Set the parentage

Q – Multiple application concurrently access the same database

U – Moving forward to the database when unqualified GN and GNP functions used

V -

NULL – Reserves one or more positions in an SSA into which command codes can

Place dynamically.

Unqualified SSA with an F command code performs faster than GU CALL because

GNP with the F command code takes advantage of the current position.

ABEND codes:

U0260 – Parm count value is less than the parameter list count.

U0456 – PSB is not found in the ACBLIB