Before you begin: You should determine the following before converting to a multicluster CDS:

1. The amount of disk space required.
2. The number of volumes that are needed. Each volume will be a VSAM cluster.
3. The key range for each cluster. See Determining key ranges for a multicluster control data set.

Perform the following steps to convert a CDS to a multicluster CDS.

1. Review Considerations for using multicluster control data sets.
2. Stop DFSMShsm on all z/OS images.
3. Back up the CDS you are converting using the access method services (AMS) EXPORT command.
4. Define a new multicluster CDS using the AMS DEFINE CLUSTER command. For a sample definition, see Figure 1.
   Figure 1. Sample Definitions for a Multicluster (2 clusters) MCDS and BCDS

   //HSMCDS   JOB ,MSGLEVEL=(1,1)
   //***************************************************************/
   //* SAMPLE JCL THAT ALLOCATES MULTICLUSTER CONTROL DATA SETS.   */
   //***************************************************************/
   //*
   //STEP1    EXEC PGM=IDCAMS,REGION=512K
   //SYSPRINT DD SYSOUT=A
   //SYSUDUMP DD SYSOUT=A
   //SYSIN DD *
    DEFINE CLUSTER (NAME(DFHSM.MCDS1) -
        STORAGECLASS(SCLASS1) -
        CYLINDERS(2)  -
        RECORDSIZE(200 2040) FREESPACE(0 0) -
        INDEXED KEYS(44 0) SHAREOPTIONS(3 3) -
        UNIQUE LOG(NONE)) -
      DATA -
        (NAME(DFHSM.MCDS1.DATA) -
        CONTROLINTERVALSIZE(4096)) -
      INDEX -
        (NAME(DFHSM.MCDS1.INDEX) -
        CONTROLINTERVALSIZE(4096))
     DEFINE CLUSTER (NAME(DFHSM.MCDS2) -
        STORAGECLASS(SCLASS1) -
        CYLINDERS(2)  -
        RECORDSIZE(200 2040) FREESPACE(0 0) -
        INDEXED KEYS(44 0) SHAREOPTIONS(3 3) -
        UNIQUE LOG(NONE)) -
      DATA -
        (NAME(DFHSM.MCDS2.DATA) -
        CONTROLINTERVALSIZE(4096)) -
      INDEX -
        (NAME(DFHSM.MCDS2.INDEX) -
        CONTROLINTERVALSIZE(4096))
    DEFINE CLUSTER (NAME(DFHSM.BCDS1) -
        STORAGECLASS(SCLASS1) -
        CYLINDERS(2)  -
        RECORDSIZE(334 6544) FREESPACE(0 0) -
        INDEXED KEYS(44 0) SHAREOPTIONS(3 3) -
        UNIQUE LOG(NONE)) -
      DATA -
        (NAME(DFHSM.BCDS1.DATA) -
        CONTROLINTERVALSIZE(12288)) -
      INDEX -
        (NAME(DFHSM.BCDS1.INDEX) -
        CONTROLINTERVALSIZE(2048))
    DEFINE CLUSTER (NAME(DFHSM.BCDS2) -
        STORAGECLASS(SCLASS1) -
        CYLINDERS(2)  -
        RECORDSIZE(334 6544) FREESPACE(0 0) -
        INDEXED KEYS(44 0) SHAREOPTIONS(3 3) -
        UNIQUE LOG(NONE)) -
      DATA -
        (NAME(DFHSM.BCDS2.DATA) -
        CONTROLINTERVALSIZE(12288)) -
      INDEX -
        (NAME(DFHSM.BCDS2.INDEX) -
        CONTROLINTERVALSIZE(2048))
    DEFINE CLUSTER (NAME(DFHSM.OCDS1) -
        STORAGECLASS(SCLASS1) -
        CYLINDERS(2)  -
        RECORDSIZE(1800 2040) FREESPACE(0 0) -
        INDEXED KEYS(44 0) SHAREOPTIONS(3 3) -
        UNIQUE LOG(NONE)) -
      DATA -
        (NAME(DFHSM.OCDS1.DATA) -
        CONTROLINTERVALSIZE(4096)) -
      INDEX -
        (NAME(DFHSM.OCDS1.INDEX) -
        CONTROLINTERVALSIZE(4096))

5. Copy the old CDS to the new multicluster CDS with the access method services REPRO command. See Figure 2 for sample JCL that copies the old CDS into the new multicluster CDS.
   Figure 2. Sample JCL that Copies the Old CDS into the New Multicluster CDS

   /*
   //******************************************************************/
   //* COPY THE OLD CONTROL DATA SETS INTO THE NEWLY DEFINED          */
   //*  MULTICLUSTER CONTROL DATA SETS.                               */
   //* NOTE: THE FROMKEY/TOKEY VALUES ARE ONLY SAMPLES.  THE ACTUAL   */
   //* PARAMETERS USED FOR THESE KEYWORDS SHOULD BE DERIVED FROM      */
   //* ACTUAL CDSS BEING USED.                                        */
   //******************************************************************/
   //*
   //STEP2    EXEC PGM=IDCAMS,REGION=512K
   //SYSPRINT DD SYSOUT=A
   //SYSUDUMP DD SYSOUT=A
   //SYSIN DD *
    REPRO INDATASET(DFHSM.MCDS) OUTDATASET(DFHSM.MCDS1) -
       FROMKEY(X'00') TOKEY(MIDDLE.KEY1)
    REPRO INDATASET(DFHSM.MCDS) OUTDATASET(DFHSM.MCDS2) -
       FROMKEY(MIDDLE.KEY2) TOKEY(X'FF')
    REPRO INDATASET(DFHSM.BCDS) OUTDATASET(DFHSM.BCDS1) -
       FROMKEY(X'00') TOKEY(MIDDLE.KEY1)
    REPRO INDATASET(DFHSM.BCDS) OUTDATASET(DFHSM.BCDS2) -
       FROMKEY(MIDDLE.KEY2) TOKEY(X'FF')
    REPRO INDATASET(DFHSM.OCDS) OUTDATASET(DFHSM.OCDS1)
   /*

6. Modify the DFSMShsm startup procedure in SYS1.PROCLIB and any other JCL (such as DCOLLECT and ARCIMPRT) that references the multicluster CDS. There must be a separate DD card for each cluster of a multicluster CDS. For more information, see Updating the startup procedure for multicluster control data sets and Updating the DCOLLECT JCL for multicluster control data sets.
7. Preallocate new CDS backup data sets if you back up your control data sets to DASD. You need backup versions for each cluster in the CDS.
   Note: Do not delete the current CDS. Instead, maintain it for a period of time until you determine that the new CDS is valid.
8. Monitor the growth of the multicluster CDS.