Changing RDDS block sizes

You can change the block size of the RDDS without bringing down IMS.

This procedure assumes that autoexport is enabled to RDDS.

To change the RDDS block size, complete the following steps:

Procedure

  1. Save a copy of the existing system RDDS by using the IEHPROGM utility with the RENAME function.
    Sample JCL is shown below.

    In the JCL, the data sets IMSPLEX1.IMS1.RDDS1, IMSPLEX1.IMS1.RDDS2, and IMSPLEX1.IMS1.RDDS3 on 3390 volumes 111111, 222222, and 333333, respectively, are renamed to SAVE.RDDS1, SAVE.RDDS2, and SAVE.RDDS3, respectively.

    //RDDSNAME JOB .........
//STEP1 EXEC PGM=IEHPROGM
//SYSPRINT DD SYSOUT=A
//DD1 DD VOLSER=111111,UNIT=SYSDA,DISP=OLD
//DD2 DD VOLSER=222222,UNIT=SYSDA,DISP=OLD
//DD3 DD VOLSER=333333,UNIT=SYSDA,DISP=OLD
//SYSIN DD *
 RENAME DSNAME=IMSPLEX1.IMS1.RDDS1,VOL=3390=111111,NEWNAME=SAVE.RDDS1
 RENAME DSNAME=IMSPLEX1.IMS1.RDDS2,VOL=3390=222222,NEWNAME=SAVE.RDDS2
 RENAME DSNAME=IMSPLEX1.IMS1.RDDS3,VOL=3390=333333,NEWNAME=SAVE.RDDS3
  2. Scratch and reallocate all RDDSs with the new block size using either TSO or the IEBGENER job provided in the DFSRDDAL skeleton JCL. The JCL is shipped in the IMS.SDFSSLIB data set.
  3. Create a dummy resource descriptor to force an autoexport at the next checkpoint by issuing the command CREATE PGMDESC NAME(DUMMY) LIKE(DESC(DFSDSPG1)).
  4. Issue the /CHE command.
  5. Delete the dummy resource by issuing the command DEL PGMDESC NAME(DUMMY).

After autoexport completes, message DFS3371I is issued to the system console, indicating that the autoexport was successful.

If IMS is terminated before autoexport successfully completes, it can be restarted with a warm or emergency restart. Both warm and emergency restarts rebuild the resource and descriptor definitions in the IMS.MODBLKS data set from the IMS log records and automatically export them to a system RDDS at the first system checkpoint.

If a cold start is necessary, perform the following steps:

  1. Rename the RDDSs to their original names by using the IEHPROGM, swapping the DSNAME and the NEWNAME data set name values.
  2. Bring up IMS and issue the IMS cold start command /NRE CHKPT 0.
  3. Change the block sizes using the procedure above.