PM02546: EXCESSIVE ECSA UTILIZATION AFTER MULTIPLE DSNL030I WITH 00D3443AAT DB2 Z/OS SERVER

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• DB2DDF DDFL09 defect pm02546 dpm02546
  ECSA short on storage condition due to a storage leak in the
  DB2 Queue Element Pool after receiving many
  DSNL030I DSNLXALC 00D3443A messages at the DB2 z server.
  This can result in accumulating storage for LWEL blocks.
  The DB2 z server is configured with SNA inbound name
  translation.
  
  If private protocol, a DSNL030I message with corresponding
  LOGREC entry 04E-00D3001D (non dumping) from DSNLTMRA will be
  present.
  
  It may be possible for the storage leak to occur with DRDA as
  well.
  Symptoms may include DSNL030I with corresponding LOGREC entry
  04E-00D30022 from DSNLTACC (non-dumping), the storage leak
  would be in the CPOOL storage pool DCRM VTAM EXITL.
  
  **************************************************************
  Additional Symptoms and keywords:
    5740XYR00
    Short on ECSA ssnmDIST DIST storage SOS
    after many occurrences of
    DSNL030I MSGDSNL030I DSNLXALC 00D3443A RC00D3443A
    accompanied by (Logrec only)
    ABEND04E AB04E S004E 04E 04E-00D3001D RC00D3001D DSNLTMRA
    ABEND04E AB04E S004E 04E 04E-00D30022 RC00D30022 DSNLTACC
  
    LCBLQREP LWEL ESCA pool
    DB2 QUEUE ELEMENT POOL
    SP231 SUBPOOL231 SUBPOOL SUB POOL 231 KEY 7 07 KEY7 KEY07
    . 04E-00E2001F, LOC=DSNSLD1.DSNSVBK+06E2
      ABEND04E AB04E S004E 04E 04E-00E2001F 00E2001F RC00E2001F
        DSNSVBK DSNSVBK+06E2 06E2
    . 878-00000004
      ABEND878 AB878 S00878 878 878-00000004 00000004 RC00000004
    . 04E-00E20022, LOC=DSNSFBK.DSNSFBK+059E
      ABEND04E AB04E S004E 04E 04E-00E20022 00E20022 RC00E20022
        DSNSFBK DSNSFBK+059E 059E
  
    LCBLXPLI LWEL z/OS CPOOL ssnmDIST pool
    DCRM VTAM EXITL
    SP230 SUBPOOL230 SUBPOOL SUB POOL 230 KEY 7 07 KEY7 KEY07
  

Local fix

• Correct DSNL030I message condition, or prevent application
  from executing.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All Distributed Data Facility (DDF) users.   *
  ****************************************************************
  * PROBLEM DESCRIPTION: Unpredictable results due to ECSA       *
  *                      short on storage condition due to       *
  *                      storage leak in the DB2 LCBLQREP        *
  *                      ("DB2 QUEUE ELEMENT POOL") storage      *
  *                      pool.                                   *
  *                      Symptoms may include:                   *
  *                        04E-00E2001F DSNSVBK+06E2             *
  *                        878-00000004                          *
  *                        04E-00E20022 DSNSFBK+059E             *
  *                      Over time, this leak may accumulate     *
  *                      to the point of affecting the entire    *
  *                      z/OS system due to the resultant        *
  *                      ECSA/CSA storage constraint.            *
  *                                                              *
  *                      A storage leak may also occur in z/OS   *
  *                      CPOOL storage related only to ssnmDIST  *
  *                      address space (LCBLXPLI).               *
  *                                                              *
  *                      The leaks only occur in very rare and   *
  *                      unlikely error scenarios such as during *
  *                      remote user authentication error        *
  *                      scenarios and DB2 z/OS thread abend     *
  *                      conditions.                             *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  If a DB2 thread abend occurs while processing a request from
  a remote client system, DB2 abend recovery processing may
  neglect to free LWEL control block storage related to the
  request. The LWEL storage may reside in a DB2 managed ECSA
  related storage pool (LCBLQREP - "DB2 QUEUE ELEMENT POOL") or
  in an ssnmDIST address space owned z/OS CPOOL storage pool
  (LCBLXPLI - "DCRM VTAM EXITL"), however the ECSA related
  storage leak may potentially impact the entire z/OS host
  rather than only the specific DB2 z/OS subsystem involved.
  The target storage of the leak, ECSA or z/OS CPOOL, depends on
  the communication protocol being used. Remote DB2 z/OS client
  systems that use DB2 Private Protocol will tend to affect ECSA
  whereas remote client systems that use DRDA protocol will tend
  to affect only z/OS CPOOL for the ssnmDIST address space.
  It should be noted that many types of DB2 z/OS detected
  authentication errors result in DB2 z/OS induced thread abend
  conditions where no dump is provided. Evidence of these abend
  conditions may only exist in z/OS LOGREC data, however the
  presence of DSNL030I message conditions, especially those
  related to some form of authentication error, may indicate a
  root source that can be prevented.
  For example, in the reported case, the root source was related
  to many occurrences of a DSNL030I DSNLXALC 00D3443A message
  condition, each of which was associated to an 04E-00D3001D
  DSNLTMRA abend (no dump) condition that was only evident in
  LOGREC data. By eliminating the root source of the DSNL030I
  message condition, users can prevent any further storage
  leakage. However, existing ECSA storage that has already been
  leaked can only be relieved by stopping and restarting DDF (a
  procedure which allows DB2 to refresh, delete and re-acquire,
  the storage pool), or by stopping DB2. Existing z/OS CPOOL
  storage, related to the ssnmDIST address space, that has
  already been leaked can only be relieved by stopping DB2.
  

Problem conclusion

• DB2 DBAT abend recovery processing has been changed to free
  LWEL control block storage related to a remote client request
  that may have been in progress when the abend occurred.
  

Temporary fix

Comments

APAR Information

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

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

  UK53327 UK53328

Modules/Macros

• DSNLQCTL
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• R810 PSY UK53327

     UP10/01/20 P F001

• R910 PSY UK53328

     UP10/01/20 P F001

Fix is available

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