Reblocking

An additional feature of the Move/Copy function is the option to reblock sequential, partitioned, indexed sequential and direct access data sets that consist of either fixed- or variable-length records.

Note: RECFM=U, LOAD LIBRARIES, cannot be reblocked.

The maximum block size to be given to the migrated data sets is specified as a limit value to Move/Copy. As each data set is migrated, it is reblocked to the largest block size less than or equal to the limit value. Either a global limit can be specified to apply to all data sets of the previous types, or different limits can be given for various combinations of device types, DSORG and RECFM. To define the different limit values, a list of reblocking entries must be placed in a member in the parmlib data set, each entry in the format as defined below.

When reblocking keyed data sets, the actual reblocked size can be less than the limit specified. If the new block size plus the key length will not fit on a track of a particular device type, CA Disk will attempt to reduce the block size. If this is not possible, the keyed data set will not be reblocked.

As an aid when doing reblocking, sysparm NOBLKMSG is provided to request explanatory messages when a data set cannot be reblocked.

Note: When the target data set is marked as reblockable as indicated by the DS1REBLK bit in the FORMAT 1 DSCB and your system is at DFP level 3.1 or higher, the use of the sysparm REBLKBIT=Y and the BLKSIZE= parameter under either MOVE or COPY are mutually exclusive.

If you would like CA Disk to reblock data sets that were allocated prior to DFP 3.1, you can use the DSCB Update Utility (described in DSCB Update Utility in the Installation Guide) to turn the DS1REBLK bit on. This will allow system defined reblocking to occur.