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DISK compress and PDS relocation


Article ID: 237903


Updated On:


DISK BACKUP AND RESTORE Disk Backup and Restore - MVS


Using DISK, it has been asked if it is possible to process the compression of any PDS dataset with a specific option that will force the creation of a newly allocated compressed file on the same volume where the source file was placed. Also, if this compress can bypass any SMS policy that would change the volume indicated in the request. 

The question is because the PDS could be a PROCLIB allocated to JES2 task and the compress on a different volume causes a broken chain under JES2 and system problems.


Release :  

Component : Disk Backup and Restore


If  the scope of the compress is to just update the directory of the PDS, it is possible to issue the SCAN command specifying the USE option as documented below: 

SCAN Command 

The SCAN command is used to select one or several data sets for compression from one or more volumes.


The presence of this parameter forces the use of the existing data set extents.  Specified allocation changes are confined to directory adjustment. The PP and SS sub parameters of the ALLOCATE= parameter are ignored and only the DD readjustment is done.

  • If the EMPTY parameter is also specified for empty data sets, the ALLOCATE= parameter to be ignored.
  • If the USE parameter is present and the sysparm value of PDSENQSH is Y, only SHARED ENQ is maintained for the data set during compression. In addition, ISPF and linkage editor enqueues are issued to preserve the data set integrity.


Disk would just update the existing data set and not allocate a new data set. 

If the directory update is not enough,  since PDS Compress uses SVC 99 (dynamic allocation) to allocate the data set according to parms on the command, whatever allocation product (like SMS or Allocate) is in use may change the volume requested by the compress, so DISK doesn't have control on that. In this case it  is necessary to update the allocation product policy used to not change the volume requested by the DISK command.