SMF EXCP Segment Processing

The
MICS Batch and Operations Analyzer
accumulates device and data set allocation statistics by processing the EXCP segments (or sections) of SMF records generated for batch job steps, TSO sessions, started tasks, USS, and APPC/MVS ASCH scheduled TPs (at the address space level). The EXCP segments of the SMF type 30 Common Address Space Work record contain both dynamic and non-dynamic allocations.
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The
MICS Batch and Operations Analyzer
accumulates device and data set allocation statistics by processing the EXCP segments (or sections) of SMF records generated for batch job steps, TSO sessions, started tasks, USS, and APPC/MVS ASCH scheduled TPs (at the address space level). The EXCP segments of the SMF type 30 Common Address Space Work record contain both dynamic and non-dynamic allocations.
The SMF type 30 record has a number of fields at the start of the record that describe the segment types present, the quantity of each segment type, and the length of each segment type. One of the segment types is the EXCP segment. The EXCP segment for an SMF type 30 record has the following format:
                         EXCP SEGMENT                   ---------------------------------                   | DC UT DA DDN BLK BSZ DCT BLKZ |                   ---------------------------------      LENGTH BYTES    1  1  2  8   4   2   4    8      Where DC   -    Device Class            UT   -    Unit Type            DA   -    Device Address            DDN  -    DD Name used to access the data set            BLK  -    Count of BLocKs issued for the device            BSZ  -    Largest BlockSiZe of the data set            DCT  -    Device Connect Time            BLKZ -    Largest BLocKsiZe > 32760
Generally, each EXCP segment represents the complete activity for one particular data set. There are several exceptions to this:
  • When a data set spans multiple volumes, there will be an EXCP segment for each unique device address that the data set occupies.
  • The SMF EXCP device activity is summarized by ddname and device address into a single EXCP segment before writing the segment to the SMF interval, step end, or job end record. This means that repeated dynamic allocation and unallocation of different data sets using the same ddname and device address will result in a single EXCP segment representing multiple data sets.
  • The SYS1.PARMLIB(SMFPRMxx) keyword DDCONS may be set to (NO) to prevent EXCP segment consolidation at the termination of a step. This will cause individual EXCP segments to be written to the SMF record even when the same ddname and device address are used in multiple dynamic allocations and unallocations.
  • The same data set may be allocated with different DDs, resulting in multiple EXCP segments.
  • EXCP segments may be suppressed for DB2 started tasks to improve performance.
When the number of EXCP segments causes the record length to exceed 32,756 bytes, SMF writes continuation type 30 records. With continuation records,
MICS
outputs each EXCP segment to a temporary data set for later summarization and inclusion into the
MICS
files.
MICS
will process a single SMF type 30 record with an assembly language program that builds a device address table.
The DETAIL timespan BATWDA observations are derived by summarizing the information in the EXCP segments by unique device address.
The step or interval level Device Allocations data elements are derived by summing the number of unique device addresses found in the EXCP segments by Device Class.
The step or interval level Data Set Allocations data elements are derived by summing the number of EXCP segments by Device Class.