PH53641: QREP ISSUES ASN0725W MESSAGE AFTER ENABLING ZHYPERLINK WRITE ON DB2 ACTIVE LOG.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• After enabling zHyperlink Write on Db2 active log, QREP capture
  task started to issue MSGASN0725W message indicating the log
  records returned from Db2 are out of order.
  .
  
  HYPERL/K
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * Db2 12 and 13 for z/OS data sharing users                    *
  * of IFCID 306 reading log data, excluding                     *
  * the users of GDPS Continuous Availability                    *
  * with zero data loss solution.                                *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * In data sharing, IFCID 306 F call log                        *
  * read requests may not return all the                         *
  * log records in the log range. This                           *
  * could result in QCAPTURE issuing                             *
  * message MSGASN0725W log out of order                         *
  * and potential data loss. The problem                         *
  * was reported in a zHyperLink                                 *
  * environment.                                                 *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Apply corrective PTF when available                          *
  ****************************************************************
  (1) There is a rare timing window where Db2 log read logic for
  IFCID 306 read request may delay reading log records from one
  of the Db2 members when zHyperLink WRITE is enabled for active
  logs. Log read logic continues to read log records from other
  members until all of them encountered their End-Of-Log (EOL).
  In a rare timing window situation, log read logic can not
  detect true EOL of the slow member and Db2 continues to read
  log records from other Db2 members in data sharing group. This
  results in Db2 log read returning log records from the slow
  member in the subsequent F call. If replication is
  Q-Replication and it detects this condition, it will issue
  MSGASN0725W message. Other applications or products may not
  detect this condition, thereby leading to other unspecified
  errors.
  (2) Today, if any application in the F call request does not
  specify starting log point as QW0306ES or QW0306ES+1, that was
  retrieved at the end of previous successful F/N call, indicated
  by reason code RC00E60812 or RC00E60813 (current documented
  interface), then it may encounter data loss unless the
  application has internal logic to detect and handle this
  condition.
  

Problem conclusion

• (1) To address this rare timing window, Db2 log read logic is
  redesigned to always stop reading log records when the first
  member in data sharing group encounters its EOL. Although this
  problem was reported when zHyperLink WRITE was enabled, it
  could occur regardless of whether zHyperLink READ or WRITE is
  enabled. Therefore, this new log read design applies to all
  IFCID 306 users. The new logic involves extra processing which
  could result in a slight increase in CPU usage where
  replication capture job is running.
  (2) Db2 will issue warning message MSGDSNI097I when it detects
  that an IFCID 306 READS F call does not adhere to the
  documented interface when specifying starting log point (start
  LRSN). Db2 will correct the starting log point specified in
  IFCID 306 READS request to avoid any data loss. MSGDSNI097I
  message will be issued only once on the Db2 console where the
  IFCID 306 application is running until Db2 is recycled. Refer
  to the DSNI097I message for further information and to correct
  the interface issue.
  

Temporary fix

• *********
  * HIPER *
  *********
  

Comments

• ×**** PE24/12/20 FIX IN ERROR. SEE APAR PH64627  FOR DESCRIPTION
  

APAR Information

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

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

  UI94929 UI94930

Modules/Macros

• DSNFIDIR DSNJRM03 DSNJW004 DSNFCDIR DSNJR103 DSNILGRX DSNIDLGR
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RC10 PSY UI94929

     UP23/12/22 P F312 ¢

• RD10 PSY UI94930

     UP23/12/22 P F312 ¢

Fix is available

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