DFSMShsm supports the FlashCopy® Incremental function
for Fast Replication copy pools. A copy pool can be designated to have an incremental backup version
by using the FCINCREMENTAL keyword on the FRBACKUP command. 
When the software and microcode requirements are met, you can use the FCINCREMENTAL keyword on
multiple FRBACKUP commands to specify that those copies are to be incremental, or add the ALL
subparameter to specify that all subsequent copy pool backup copies should also be incremental.
Once an incremental version has been established in a copy pool, the copy pool has an incremental version until either it is deleted or the FCINCRREMENTALLAST keyword is used. The volumes in a copy pool incremental version have persistent relationships with the target volumes. When a single disk version is maintained, the FlashCopy Incremental function is used each time a new disk version is created. When multiple disk versions are being maintained, then the FlashCopy Incremental function is used only for the version that was originally identified as the Incremental version by the FCINCREMENTAL keyword. All other versions are full copies. For example, if two disk versions are being maintained, then every other disk version uses the FlashCopy Incremental function.
The FCINCREMENTAL keyword is optional when creating a new incremental version. If the FCINCREMENTAL or FCINCREMENTALLAST keyword is specified, and the oldest disk generation to be overwritten to create the new version is not an incremental version, the command fails.
When a copy pool incremental version is no longer needed for a copy pool, issue FCINCREMENTALLAST
when you create the next incremental version. After the background copies for the incremental
version have completed, the persistent relationship for each volume is withdrawn. The disk version
remains recoverable. An alternative method is to delete the incremental version with the FRDELETE
command. After using either the FCINCREMENTALLAST keyword or the FRDELETE command, all future disk
versions are full copies until the FCINCREMENTAL keyword is used again. Adding the ALL subparameter to FCINCREMENTALLAST causes a new incremental of the oldest
copy to be taken, the persistent relationships of that copy to be withdrawn, and the relationships
of all other backup copies to be withdrawn after the next increment is taken of each of those
copies.
The initial establishment of a FlashCopy Incremental version creates a full copy of each volume (0-n tracks). Subsequent copies utilize the FlashCopy Incremental technology only to copy tracks from the source that have changed. This results in the background copy completing in a shorter time period.
Fast Replication incremental copy pool versions are not supported when the copy pool is defined with zero DASD backup versions. If the number of DASD backup versions in the copy pool definition is changed to zero and an incremental version exists, the subsequent FRBACKUP command fails. The incremental version must be removed by the FCINCREMENTALLAST keyword or deleted by the FRDELETE command.
If the number of versions is reduced so that an incremental version is automatically deleted, the FRBACKUP command fails. The incremental version either has to be deleted or has to be the oldest disk generation for FRBACKUP processing to be successful.