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Enable HPF support for full track operations (PJ47087)


Enable HPF support for full track operations (PJ47087)

In the z/TPF system, most single-record read and write I/Os to DASD can use High Performance FICONĀ® for z Systems (zHPF). Compared with channel command words, HPF is a more efficient protocol, which results in lower channel utilization and reduces I/O response time. However, full-track read and write operations currently do not use HPF translation.

The following examples use full-track operations that do not get the benefit of HPF translation:

  • ZMCPY UP and ZMCPY ALL commands
  • Recovery log I/O
  • 48 KB keypoint I/O
  • Prime dupe module comparisons (ZMCMP)
  • Capture and restore DASD I/O

By applying APAR PJ47087 all the previously mentioned full-track operations can use HPF translation, if HPF is supported by the hardware. The use of HPF translation reduces channel utilization and I/O response time because of the more efficient transport mechanism. No configuration or applications changes are required to use this support.

Lab testing

To show how using this APAR can benefit utilities and functions that perform full-track operations, we tested ZMCPY UP with and without this APAR applied. In tests with varying configurations, a series of ZMCPY UP commands were run on 70 KB cylinder DASD modules. With this APAR applied, we consistently observed at least a 25% reduction in time for the ZMCPY UP command to bring a 70 KB cylinder module online significantly reducing the amount of time the system is in simplex mode. In addition, a 23% reduction in channel utilization was observed, which reduced the stress on the environment while the ZMCPY UP command was running.

Your results will vary based upon your configuration and workload.

For more information about APAR PJ47087, see the APEDIT and IBM Documentation.