DFSMShsm processes FRBACKUP COPYPOOL commands serially. To maximize throughput, DFSMShsm creates the fast replication backup for the volumes in a copy pool in parallel. There are two levels of parallelism. The first level is that DFSMShsm invokes DFSMSdss with the PARALLEL option and up to 254 volume pairs. The second level of parallelism is the number of DFSMSdss invocations that DFSMShsm processes concurrently. DFSMShsm processes between 1 and 64 DFSMSdss invocations concurrently, the default being 15. The number of concurrent DFSMSdss invocations that are processed and the number of parallel volumes passed to DFSMSdss can be modified with the SETSYS MAXCOPYPOOLTASKS(FRBACKUP(nn) DSS(nnn)) command.