Improving performance when using IOSFBA services

It is possible to improve performance of the IOSFBA service by using the IOTOKEN keyword. The IOTOKEN keyword allows the caller to supply the address of a 32-byte area that will be used by the IOSFBA service to save information between IOSFBA service calls.

Performance may also be improved if a channel program can be reused. This is possible if all of the following conditions are true:

The storage buffers and target blocks of the z/OS FBA devices are exactly the same.
The address space where the program is located is non-swappable across all IOSFBA READ/WRITE requests.
The storage buffers remain fixed pages across all IOSFBA READ/WRITE requests.

When this is the case, the REUSECP keyword can also be used. REUSECP in combination with the IOTOKEN keyword allows the IOSFBA READ/WRITE service to simply start the channel program without a channel program build.

More than one IOTOKEN can be used by calling programs if parallel IOSFBA invocations are used, if different channel programs must be built, or if different storage buffers or z/OS FBA device target blocks are used.

If IOTOKEN is used, the IOSFBA CLEANUP service must also be used to ensure that storage is properly released. The program must call IOSFBA CLEANUP for each IOTOKEN that was used.

Using more that one device for each IOSFBA READ/WRITE operation also helps to improve overall I/O throughput.