Offload workload to zIIP processors

IMS HP Image Copy supports the IBM® System z® Integrated Information Processor (zIIP) to offload eligible database workloads to zIIP processors.

Data compression and decompression is one of the most CPU-intensive workloads in IMS HP Image Copy processes. By enabling the zIIP support with the ZIIPMODE keyword, you can use the zIIP processor to run the data compression and decompression workloads.

For the Image Copy function, the workload to create compressed image copies is run by zIIP processors if all of the following conditions are met:
  • The Image Copy function is invoked by DFSUDMP0 (zIIP processor is not supported when the function is invoked by DFSRRC00)
  • ZIIPMODE=COND is specified for the PARM keyword
  • Image Copy compression is enabled (Y is specified on position 39 of the SYSIN control statement)

The CPU time consumed on zIIP processors is notified by message FABJ0426I.

Requirements: The following requirements must be met to enable zIIP processors:
  • The SGLXLOAD library of IMS Tools Base is added to the STEPLIB DD statement of the JCL.
  • The SGLXLOAD library is APF-authorized.

Considerations before using zIIP processors

Before using the zIIP processors, consider and estimate the performance impact of using zIIP processors:

  • Using zIIP processors to run eligible workload requires overhead, especially in elapsed time of the job. If you use zIIP processors, you must test the performance impact in the test system before using them in the production system.
  • Using zIIP processors requires overhead in CPU time. Therefore, the use of zIIP processors is beneficial only if the amount of offloaded CPU time is larger than the amount of overhead CPU time. When both of the following conditions are true, specifying ZIIPMODE=COND, in many cases, results in an increase in CPU time:
    • Image copies are created on tape volumes
    • IDRC is enabled on a tape subsystem

Under these conditions, the amount of CPU time consumed for the compression routine is not large because compression process is mostly done by hardware, not software. Therefore, the amount of CPU time that is offloaded to zIIP processors is quite small. The additional (overhead) CPU time to use zIIP processors can overwhelm the CPU time that is offloaded to zIIP processors.