SMF Data Recording
SMF can record data in two ways:
- The standard and classical way: Using buffers the SMF address space, together with a set of preallocated datasets (VSAM datasets) to use when a buffer fills up. The standard name for the datasets is SYS1.MANx, where x is a numerical suffix (starting from 0).
- The relatively new way: Using log streams. SMF utilizes System Logger to record collected data, which improves the writing rate and avoids buffer shortages. It has more flexibility, allowing the z/OS system to straightforwardly record to multiple log streams, and (using keywords on the dump program) allowing z/OS to read a set of SMF data once and write it many times.
Both the two ways can be declared for the use, but only one is used at a time in order to have the other as a fallback alternative.
This data is then periodically dumped to sequential files (for example, tape drives) using the IFASMFDP SMF Dump Utility (or IFASMFDL when using log streams). IFASMFDP can also be used to split existing SMF sequential files and copy them to other files. The two dump programs produce the same output, so it does not involve changes in the SMF records elaboration chain, other than changing the JCL with the call of the new dump utility.
Read more about this topic: IBM System Management Facilities
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