Making Sense of the Many I/O Count Fields in SMF | Cheryl Watson's Tuning Letter

Discover why different fields in SMF records have different values

SMF is often used as an example of a z/OS capability that is still unmatched by other platforms. Even diehard UNIX or Windows fans salivate when they see the insights SMF provides into what is happening on z/OS. The SMF manual contains over 1000 pages of descriptions of the information provided in SMF records – and that doesn’t even include information about SMF records created by CICS, Communication Server, Db2, MQ, or WebSphere.

In this reprint from Cheryl Watson’s Tuning Letter 2024 No. 1, Todd Havekost, Senior Consultant at IntelliMagic, demonstrates how SMF data can serve as a valuable learning tool. Using the example of multiple SMF fields that seem to report I/O rates but often contain significantly different values, Todd’s structured approach to comparing these fields and investigating their contents not only provides crucial information for users but also shows how combining SMF data with an inquisitive mindset can uncover unique insights into the inner workings of z/OS.

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