When only installing CA Compress for IMS, the UNLOAD job running with IBM version of DFSRRC00 fails with abend U4004. Why?

To install just CA Compress for IMS only the following FMIDs are required:

CITKG00 /* IMS Toolkit Common Component */ 

CASTG00 /* CA Compress Data Compression for IMS */

If the UNLOAD job for example

UNLOAD EXEC PGM=DFSRRC00,PARM='ULU,DFSURGU0,&DBD,,,,,,,,,,,&DBRC',

STEPLIB DD DSN=CAIMS.SHRINK.IMSUT.LOAD,DISP=SHR

DD DSN=IMS.IMSYSSxy.SDSFRESL,DISP=SHR

DD DSN=IMS.PRD.EXIT.RESLIB,DISP=SHR

DD DSN=IMS.PRD.RESLIB,DISP=SHR

then executed it fails with U4004 on step UNLOAD:

+IDI2302E MODULE "IDIDBOM " COULD NOT BE FOUND IN THE LIBRARY 00040000).

+IDI5603E UNABLE TO LOAD SUFFIXED LOAD-MODULE: IDIDBOM . RC=08

IEF450I IMSICUOF UNLOAD UNLOAD - ABEND=S000 U4004 REASON=00000000 371

The UNLOAD job can only be run successfully when the IBM version of DFSRRC00 region controller is called and not IDIDBO. This can be achieved by moving the CA Compress Data Compression for IMS (SHRINK) loadlib to the last position in STEPLIB concatenation.

The module reported in the IDI2302E error message will be suffixed dependent on the version of IMS installed in this environment.

For example:

IDIDBOJ - IMS v11

IDIDBOK - IMS v12

IDIDBOL – IMS v13

IDIDBOM – IMS v14