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

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You can track all active APARs for this component.

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 number

    II07124

  • Reported component name

    PB LIB INFO ITE

  • Reported component ID

    INFOPBLIB

  • Reported release

    001

  • Status

    CLOSED CAN

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    1993-07-08

  • Closed date

    1997-10-24

  • Last modified date

    2010-02-10

  • 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



Document information

More support for: z/OS family

Software version: 001

Operating system(s): MVS

Reference #: II07124

Modified date: 10 February 2010


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