PI74703: U0847 C2C83012 DFSDBH30 PGSL7700

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• ABENDU0847 return code C2C83012 was issued from module DFSDBH30
  during dynamic backout processing.  This abend was added by a
  prior apar to prevent a loop in DFSDBH30 at label PGSL7700 due
  to an invalid unsorted purgeable buffer ( IBF ) chain.
  .
  The following execution sequence produces the U0847 C2C83012:
  .
  1)  Several partitions were performing concurrent REPL calls
      against a HALDB database in the midst of frequent pseudo-
      abends caused by U3303 (partition unavailable) and U4087
      (appl) abends.
  2)  The pseudoabends caused Dynamic Backout to run for each
      region to back out the updates made by the REPL calls
  3)  DFSDLR00 called DFSPSEL0 to VERIFY PARTITIONED DATABASE
      ACCESS and SELECT a SPECIFIC PARTITION BASED UPON the KEY.
  4)  Routine DFSPSEL1 called DFSDBAU0 via PSAUTH to AUTHORIZE/
      CHECK the PARTITION.
  5)  The Syslog revealed a "FOI110I  /STO DB GDDCDAF LOCAL"
      command had been issued in the middle of the REPL calls
      which made the partition UNAVAILABLE and returned STATUSBA
  6)  "FA EXIT FOR IMS U4087 ABENDS INVOKED" was also found in
      the Syslog, which triggered a pseudoabend of IMS REGION
  6)  DDIRNOSC (STOPPED DUE TO PREVIOUS ERR) was set ON and
      caused authorization to fail with a RC12 (x'0C').
  7)  Execution returned to DFSPSEL0 which changed RC12 to RC8
      for the AUTH FAILURE and set R0 to x'4020' and R2 to RC4.
  8)  Since authorization failed for partition GDDCDAF, DSGAMPA
      was updated in the DSG, but DSGDMBNO was left unchanged.
  9)  Dynamic Backout got control to back out updates made by
      the REPL calls prior to the partition becoming UNAVAILABLE
  10) Logic in routine LOCDSG in backout module DFSRDBC0
      verified the AMP in DSGAMPA matched the partition in the
      log record to be backed out.  However, the DMB number in
      DSGDMBNO was not verified and was passed to DFSDBH10 for
      the Buffer Purge (x'E5')call to write the altered buffer.
  11) At this point,  DFSDBH10 calls STEALBFR with the invalid
      DSGDMBNO and the HASH routine creates a duplicate buffer
      prefix, with different DMB numbers, but the same block,
      UCBAD, and CCHHR values.  The U0847 C2C83012 is issued.
  The fix in this APAR will resolve both the original LOOP
  as well as the U0847 C2C83012 abend that result from two
  OSAM buffer prefixes containing the same IBFCBLK, IBFUCBAD,
  and IBFCCHH2, but different IBFCDMB values.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All IMS V15 QPP Full Function OSAM HALDB Database users.     *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * ABENDU0847 return code C2C83012 was issued from module       *
  * DFSDBH30 during Dynamic Backout processing. This abend       *
  * was added by a prior apar to prevent a loop in DFSDBH30 at   *
  * label PGSL7700 due to an invalid unsorted purgeable buffer   *
  * ( IBF ) chain.                                               *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * INSTALL CORRECTIVE SERVICE FOR APAR/PTF                      *
  ****************************************************************
  The following execution sequence produces the U0847 C2C83012:
  
  1)  Several partitions were performing concurrent REPL calls
       against a HALDB database in the midst of frequent
       pseudoabends caused by U3303 (partition unavailable) and
       U4087 (appl) abends.
  
  2)  The pseudoabends caused Dynamic Backout to run for
       each region to back out the updates made by the REPL calls.
  
  3)  DFSDLR00 called DFSPSEL0 to VERIFY PARTITIONED
       DATABASE ACCESS and SELECT a SPECIFIC PARTITION
       BASED UPON the KEY.
  4)  Routine DFSPSEL1 called DFSDBAU0 via PSAUTH to
       AUTHORIZE/CHECK the PARTITION.
  
  5)  The Syslog revealed a "FOI110I  /STO DB GDDCDAF LOCAL"
       command had been issued in the middle of the REPL calls
       which made the partition UNAVAILABLE and returned
       STATUSBA.
  6)  "FA EXIT FOR IMS U4087 ABENDS INVOKED" was also found in
       the Syslog, which triggered a pseudoabend of IMS REGION.
  7)  DDIRNOSC (STOPPED DUE TO PREVIOUS ERR) was set ON and
       caused authorization to fail with a RC12 (x'0C').
  8)  Execution returned to DFSPSEL0 which changed RC12 to RC8
       for the AUTH FAILURE and set R0 to x'4020' and R2 to RC4.
  9)  Since authorization failed for partition GDDCDAF, DSGAMPA
  was
       updated in the DSG, but DSGDMBNO was left unchanged.
  10) Dynamic Backout got control to back out updates made by the
        REPL calls prior to the partition becoming UNAVAILABLE.
  11) Logic in routine LOCDSG in backout module DFSRDBC0 verified
        the AMP in DSGAMPA matched the partition in the log record
  to
        be backed out.  However, the DMB number in DSGDMBNO was
        not verified and was passed to DFSDBH10 for the Buffer
  Purge
        (x'E5')call to write the altered buffer.
  12) At this point,  DFSDBH10 calls STEALBFR with the invalid
        DSGDMBNO and the HASH routine creates a duplicate buffer
        prefix, with different DMB numbers, but the same block,
  UCBAD,
        and CCHHR values.  The U0847 C2C83012 is issued.
  
  The fix in this APAR will resolve both the original LOOP as
  well as the U0847 C2C83012 abend that result from two
  OSAM buffer prefixes containing the same IBFCBLK,
  IBFUCBAD, and IBFCCHH2, but different IBFCDMB values.
  

Problem conclusion

• Code has been modified / added in the following modules to
  correct the reported problems:
  
  DFSPSEL0
  Code has been inserted after label PS1E300 to add the
  partition DMB number, ID, and REORG number to the
  partition DSG. DSGLROOT is cleared and  DSGSETLR is
  reset to match the DSG settings for similar authorization
  errors at labels PS2E300 and PS3E300.
  
  DFSRDBC0
  Code has been inserted after label LOCDSG1 to add an
  additional check to verify if the partition DSGDMBNO
  matches DDIRNUMB.   If they match, the JCBDSG will be
  used.  If they don't match, a branch is taken to BUILDDSG
   to build a temporary DSG for DYN BKO to use.
  

Temporary fix

Comments

APAR Information

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

  PI70071

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

  UI45622

Modules/Macros

• DFSPSEL0 DFSRDBC0
  

Fix information

• Fixed component name

  IMS V15

• Fixed component ID

  5635A0600

Applicable component levels

• R500 PSY UI45622

     UP17/03/25 P F703

Fix is available

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