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Dispatching Priorities and SMF 30 Records



Document Author:

Kathy Walsh


Document ID:

TD100201


Doc. Organization:

Advanced Technical Sales


Document Revised:

08/24/2003


Product(s) covered:

OS/390







Abstract: Customers using the SMF 30 records should be aware of situations where the dispatching priority set in the records are incorrect.

Subtypes 3, 4, and 5 of the SMF 30 records will record incorrect information in the SMF30PTY field. In compatibility mode the field will contain x’09’, while in goal mode the field will contain x’00’.
There is an APAR, OY20300, closed SUG in 1989 which describes this problem for compatibility mode systems. The incorrect data happens because at the time the SMF 30 subtype 3, 4, and 5 records are written the initiator does not have access to the ASCBDP which contains the actual dispatching priority.

Subtype 2 of the SMF 30 record does have access to the ASCB and hence the dispatching field in SMF30PTY is correct. So for long running address spaces, like system started tasks the information is correct.

Below is an example of what may be seen when processing the SMF 30 records.

 MONTH DAY  HOUR  PGN JOBNAME       PTY   CPU
                                           %
 *******************************************
 MAY    12  8.00   10 FTPSRV1      142   0.0
 MAY    12  9.00   10 FTPSRV1      142   0.1
 MAY    12 10.00   10 FTPSRV1      142   0.1
 MAY    12 11.00   10 FTPSRV1      142   0.0
 MAY    12 12.00   10 FTPSRV1      142   0.3
 MAY    12 13.00   10 FTPSRV1      255   0.0
 MAY    12 14.00   10 FTPSRV1      142   0.0
 MAY    12 15.00   10 FTPSRV1      255   0.0
 MAY    12 16.00   10 FTPSRV1      142   0.0
 MAY    12  8.00   10 FTPSRV2        9   0.0
 MAY    12  9.00   10 FTPSRV2        9   0.1
 MAY    12 10.00   10 FTPSRV2        9   0.0
 MAY    12 11.00   10 FTPSRV2        9   0.0
 MAY    12 12.00   10 FTPSRV2        9   0.0
 MAY    12 13.00   10 FTPSRV2        9   0.0
 MAY    12 14.00   10 FTPSRV2        9   0.0
 MAY    12 15.00   10 FTPSRV2        9   0.0
 MAY    12 16.00   10 FTPSRV2        9   0.0


The FTPSRV* address spaces are created dynamically to handle forked processes. FTPSRV1 was present all day, which can be confirmed by checking the JES job number to ensure it is the same iteration of the address space. FTPSRV2, was not present all day, but an address space of this name was found at different points throughout the day, again this was verified by seeing different JES job numbers. Since the address space was not present, SMF 30 subtype 2 records were not cut and so the dispatch priority was incorrectly reported.



Classification:

Software

Category:

Performance




Platform(s):

IBM System z Family

S/W Pillar(s):

IBM System z Software

O/S:

OS/390

Keywords:

SMF, SMF30PTY

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