Allocating a COMMDS

The following access method services job allocates a 1-track COMMDS;

  //STEP  EXEC PGM=IDCAMS
  //SYSUDUMP DD SYSOUT=*
  //SYSPRINT DD SYSOUT=*
  //SYSIN    DD *
    DEFINE CLUSTER(NAME(SMS.COMMDS1.COMMDS) LINEAR VOL(SMSVOL) -
    TRK(1 1) SHAREOPTIONS(3,3)) -
    DATA(NAME(SMS.COMMDS1.COMMDS.DATA)REUSE)
  /*

This job creates a VSAM linear data set named SMS.COMMDS1.COMMDS.

The COMMDS must reside on a shared volume accessible from all systems in the SMS complex. To ease recovery in case of failure, the COMMDS should reside on a different volume than the ACDS. Also, you should allocate a spare COMMDS on a different shared volume. Recovering Storage Management Subsystem information provides additional information on the backup and recovery of control data sets. The control data set (ACDS or COMMDS) must reside on a volume that is not reserved by other systems for a long period of time because the control data set (ACDS or COMMDS) must be available to access for SMS processing to continue.

Recommendations:

Specify the REUSE option when defining the COMMDS data set to help avoid space problems (SMS reason code 6068) during subsequent COMMDS updates or IMPORT/EXPORT functions.
The COMMDS and ACDS must be accessed from all systems in the complex simultaneously.