ARCCDEXT is called for both system- and non-system-managed data sets that are eligible for DFSMShsm-controlled reblocking. A flag (DS1SMSFG) in the data set VTOC entry indicates the type of data set being processed.

After the DFSMShsm data set reblock exit has been called, DFSMShsm checks the parameter list to determine if you requested reblocking. If DFSMSdss is the data mover for recall or recovery and DFSMShsm determines that you have requested reblocking, DFSMShsm tells DFSMSdss to reblock the data set subject to its ADRREBLK exit. The DFSMSdss ADRREBLK exit is preloaded with a default that allows the system to determine the blocksize. You can override the system-determined block size by specifying a different blocksize in the ADRREBLK exit. Although ADRREBLK can be coded to specify an explicit blocksize, it is recommended that you use the default implementation (system-determined block size for the optimal block size value).

Changing the ADRREBLK exit affects all jobs that invoke DFSMSdss restore.

For detailed information about the DFSMSdss ADRREBLK exit, see Reblock Installation Exit Routine (ADRREBLK).

The ARCCDEXT routine must be reentrant.