Restoring direct access data sets

When DFSMSdss restores direct data sets, several processing options can be used. Direct data sets can be organized by relative block address or by track-track record (TTR).

Relative block addressable direct access data sets can be processed block by block to like and unlike target devices if the block size fits on the target track. When the data sets are processed block by block, DFSMSdss updates the block reference count of dummy records contained in the relative block addressed direct access data sets. To process block by block, the direct access data sets must have neither a variable record format nor a standard user label.

TTR direct access data sets may become unusable if they are processed block by block. TTR and relative block addressable data sets can be processed track by track to like and unlike target devices whose track capacity is equal to or greater than the source. Block by block processing is more efficient because track by track processing to an unlike device of larger track capacity can leave some unused space on each track of the target data set.

Several DFSMSdss keywords implement the BDAM processing options:

AUTORELBLOCKADDRESS: If the data set is accessed with Optional Services Code (OPTCD) indicating relative block addressing, it is processed as if it were specified in the RELBLOCKADDRESS subkeyword list, and processing is block by block. If your installation has many relative block address direct access data sets, you can use the DFSMSdss installation options exit to turn on the AUTORELBLOCKADDRESS function.
RELBLOCKADDRESS: If the data set is specified in the subkeyword list, the data set is processed block by block.
TTRADDRESS: If the data set is specified in the subkeyword list, the data set is processed track by track.
FORCE: If the track capacity of the receiving volume is smaller than the source, FORCE may be required for variable or undefined length TTR-organized direct access data sets. These data sets may be unusable after restore and, if possible, should be restored to a like device. Use RELBLOCKADDRESS to restore relative block address direct access data sets to unlike devices.

Note: If you do not specify a keyword, data is moved to the target on a track by track basis.

For more information about using BDAM processing options with DFSMSdss keywords, refer to RESTORE command for DFSMSdss.

For more information about the installation options exit, refer to z/OS DFSMS Installation Exits.

For information about using DFSMS macros for non-VSAM data sets, refer to z/OS DFSMS Macro Instructions for Data Sets.