You can optimize Compatible FlashCopy® volumes by using the DFSMSdss utility DEFRAG command with the FASTREPLICATION option. See IBM® z/OS® DFSMSdss Storage Administration for details on the FASTREPLICATION option.
CAUTION:
When all of the following
conditions are met, copying a dataset becomes slow. Then, copying of the next dataset
starts while the other dataset is being copied, which might result in a
DEFRAG command error.
- The parity group to which the volume belongs is overloaded by I/O requests.
- The DEFRAG command is executed with the FASTREPLICATION(REQUIRED) option.
To avoid a DEFRAG command error, either do not specify the FASTREPLICATION option or specify FASTREPLICATION(PREFERRED). They both have the effect of attempting to execute Compatible FlashCopy® and, if it cannot run, to run Concurrent Copy or a host copy operation. If you specify FASTREPLICATION(REQUIRED), and you receive an error, reduce the workload on the parity group.