Forcing the use of preallocated VSAM data sets (PN04574)

You can force the use of preallocated VSAM data sets by setting the flag at offset X'08' in ADRPATCH. The settings are:

X'00': DFSMSdss functions normally, deleting and reallocating VSAM data sets, as necessary, before restoring data to them.
Any setting other than X'00': During a logical RESTORE of VSAM data sets to preallocated targets, DFSMSdss unconditionally uses the preallocated data sets without deleting and reallocating them. DFSMSdss also assumes the targets are reusable and resets the high use RBA to 0 during OPEN if the target data sets are not empty. You can ensure that the preallocated targets are defined using the REUSE attribute.

Note: If you want DFSMSdss to restore a single-volume VSAM data set to multiple volumes, the preallocated target data set must have the reusable attribute and have data allocated across multiple primary volumes. DFSMSdss will not recognize candidate volumes.

To set the flag to on dynamically, use the SET PATCH command. To set the flag to on (for example, X'FF') permanently, modify the sample JCL (see Sample JCL) as follows:

//SYSIN DD *
   NAME ADRDSSU ADRPATCH
   VER   08        00
   REP   08        FF