II07124: DB2 DBM1 HIGH CPU UTILIZATION IN SMFEXIT IEFTB728 OR IEFTB726 CICS TRANSACTIONS IN I/O WAIT.

APAR status

• Closed as canceled.

Error description

• The DB2 DBM1 address space is in a processing LOOP with
  abnormally high CPU usage for 1 to 5 minutes at 60 minute
  intervals.  All DB2-related CICS transactions are in I/O WAIT.
  A GTF trace for DBM1 shows only timer pops, and the PSW points
  to IEFTB728.  This is the SMF Type30 record handler module.
  This situation is fully described in the following MVS APARs:
          OY10189, OY25606, OY31613, OW00884 .
       There is a higher possibility that the problem will occur
  when DB2 is in use because DB2 can have up to 100000 data sets
  open simultaneously.  The solution is to code either DDCONS=NO
  (YES is the default) or INTERVAL(240000) (24 hours, 0 minutes,
  0 seconds) in the MVS SMFPRMxx member.
  
       Having a lot of SMS candidate volumes can also cause high
  CPU utilization since SMF creates an EXCP section for every
  candidate volume as well as volumes currently in use.  SMS
  candidate volumes can be specified via a static volume count or
  Dynamic Volume Count (DVC) in the DATACLAS.
  
  Additional symptoms: SLOW DB2 shutdown when DETAIL is used.
  Circumvention is to use NODETAIL .
  .
  Note: if you code DDCONS=NO, you will eliminate one part of
        this SMFexit concern.  Setting the INTERVAL to 24 hours
        is not always a practical thing to do.  The object of the
        EXIT is to capture performance related information.  A
        once a day capture would not be of any good use.  1 hour
        is probably the most that you would want to set for the
        EXIT.
  
       With DETAIL set, the exit will acquire 32k blocks of sp230
  to house DD and EXCP information. These blocks will stay around
  throughout the life of the owning address space (DBM1).  DB2
  restart is required to clear/free the 32k blocks of subpool230.
  Within a few days, sp230 in DBM1 may grow to 100s of millions
  of bytes.  If DB2 stays up for a prolonged period of time,
  1-2 weeks, various out of Private storage conditions like:
     ABEND80A, ABEND878, ABEND106, ABEND04E rc00E20003 rc00E200xx
  will intermittently, then solidly occur as DBM1 gradually runs
  out of ALL private area storage, HIGH and then LOW.
     Use this SMFEXIT with care.
  
  Note in regards to DETAIL vs NoDETAIL:  The option of
       specifying NODETAIL and INTERVAL in the SYS1.Parmlib
       SMFPRMxx member would cause the EXCP section not to be
       written out to the Type30 subtype4 and subtype5 records,
       but it would still write the info out in Type30 subtype2
       and subtype 3 records.  The difference is that the st2 and
       st3 records are written out after each interval while in
       the st4 and st5 the data is retained in the address space.
       The change for the accounting package would be that they
       would need to collect the subtype 2 and 3 records to get
       the same info from the one subtype 4 record.
  
  Additional note for DETAIL vs NODETAIL:
       If the DB2 address space is run as a batch job, then the
  INTERVAL and NODETAIL options will have no effect.  If the DB2
  address space is run as a started task (STC) then either the
  INTERVAL and NODETAIL options must be put on the SYSSTC
  parameter, or the SYSSTC parameter must inherit those options
  from the SYS parameter.
  
  ------------
  JBW
  
  z/OS 1.10 has a new option:
  EMPTYEXCPSEC{(NOSUPPRESS)}
                   {(SUPPRESS)  }
  Specifies whether or not you want to suppress empty execute
  channel program (EXCP) entries in the SMF type 30 record.
  
  NOSUPRESS:
    This is the default. It specifies that the system
  generate anempty SMF type 30 record EXCP section for
  for each SMS candidate volume in the storage group which
  was not allocated to the DD statement.
  SUPRESS specifies that the system suppress the creation of empty
  EXCP sections for non-allocated candidate volumes in the SMS
  storage group.
  
  For this option you should review APAR  OA29582
  INCOMPLETE DOCUMENATION DESCRIBING THE AFFECTS OF THE
  EMPTYEXCPSEC(SUPPRESS) SMFPRMXX PARMLIB OPTION
  Customer can review the SMS option to see if any changes
  to the volume count if the vast amount of EXCP records
  suddenly occurs. They can change back the volume count
  or use the new EMPTYEXCPSEC option to reduce the dummy entries.
  Or use NODETAIL and INTERVAL to surppress all of the excp
  sections in the type30 subtype4&5 to reduce storage usage
  in the address space.
  When the new option EMPTYEXCPSEC(SUPPRESS) is used, when there
  are a large amount of data sets that are open and how long these
  data sets stay open, customer can still run into storage
  shortage condition with the EXCP entries that are valid.
  Customer can also review the volume count option in the STORCLAS
  and DATACLAS profile to see if any recent changes that can
  account for the issue.
  Additional keywords: SMF DB2 SMFPRMxx INTERVAL DDCONS SMFTYPE30
                       5740XYR00 DB2INFO  E6007FF4
                       CLKC IEEMB836 . IEFTB728  in SYSTRACE
                       KEY0 SP230 Subpool230
  

Local fix

Problem summary

Problem conclusion

Temporary fix

Comments

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APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

Applicable component levels