Creating the RCDS

The three RCDSs are linear VSAM data sets. They contain identical copies of essential information CICS® VR needs to recover your VSAM spheres.

To reduce the possibility of losing all three copies of the RCDSs, IBM® recommends that you create each RCDS on separate volumes, disk controllers, and channels. In addition, your VSAM spheres must be on different volumes, disk controllers and channels from your RCDSs. These precautions prevent a single hardware failure from making all three RCDSs unusable, or from making the RCDS and the VSAM sphere to be recovered unusable. CICS VR regularly checks the consistency of data between the three data sets. If one or two of the RCDSs are temporarily lost, for example; the unavailability of a disk path, CICS VR automatically copies the data from the remaining RCDS the next time the other data sets are available.

The sample AMS commands to define three RCDSs:
Figure 1. AMS Commands to define the CICS VR RCDS
 //ALLOC    EXEC PGM=IDCAMS
 //SYSPRINT DD SYSOUT=*
 //SYSIN    DD *
   DEFINE CLUSTER                                -
       (NAME('DWW.DWWCON1')                      -
        VOLUMES(TSOL01)                          -
        CYLINDERS(60 20)                         -
        LINEAR                                   -
        SHR(3 3))

   DEFINE CLUSTER                                -
       (NAME('DWW.DWWCON2')                      -
        VOLUMES(TSO007)                          -
        CYLINDERS(60 20)                         -
        LINEAR                                   -
        SHR(3 3))

   DEFINE CLUSTER                                -
       (NAME('DWW.DWWCON3')                      -
        VOLUMES(TSOL02)                          -
        CYLINDERS(30 20)                         -
        LINEAR                                   -
        SHR(3 3))
 /*