DFSMShsm can process up to 64 volume recovery from dump tasks concurrently. The MAXDUMPRECOVERTASKS parameter of the SETSYS command defines the maximum number of volume recovery from dump tasks that can be concurrently processed. The default value is 1. A value greater than 1 must be specified to allow multi-tasked volume recovery from dump tapes. The MAXDUMPRECOVERTASKS value specified becomes the maximum number of simultaneous volume recovery tasks that can be processed using the FRRECOV and RECOVER commands. When recovering volumes without using fast replication, multiple RECOVER commands must be issued to take advantage of multi-tasked volume recovery from dump.
SETSYS MAXDUMPRECOVERTASKS(64)In the above example, the maximum number of concurrent volume recovery from dump tasks is 64. This allows you to issue multiple RECOVER commands and that those commands can be processed concurrently (a maximum of 64 concurrent volume recovery tasks). In addition, it also allows a single FRRECOV command to initiate up to 64 concurrent recovery operations from tape.
To decide how many concurrent volume recovery from dump tasks DFSMShsm should process, consider how many tape drives are available. If any dump class involved is defined with a STACK value of more than 1, DFSMShsm writes multiple dump copies sequentially as each tape is mounted for that dump class. The maximum level of parallelism for multi-tasked recovery is limited by how volumes are stacked on the dump tapes. If all volumes being recovered are stacked on a single tape, then only a single recovery task will be started for those volumes. The reduced parallelism might lengthen the total time needed for the volume recovery to complete.