PI04990: LOG DATA NOT ALWAYS WRITTEN BEFORE DB UPDATED.

APAR status

• Closed as program error.

Error description

• OSAM DB buffer purge does not always guarantee log data for DB
  updates is hardened before the DB is updated.  A crash after
  such an event can result in a broken DB.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All IMS V13 OSAM database users              *
  ****************************************************************
  * PROBLEM DESCRIPTION: DB updates not logged before DB itself  *
  *                      updated.  IMS failure at this point can *
  *                      result in a broken DB after restart.    *
  ****************************************************************
  * RECOMMENDATION: INSTALL CORRECTIVE SERVICE FOR APAR/PTF      *
  ****************************************************************
  Subroutine PGLOGCNT in the OSAM buffer purge routine DFSDBH30
  assumed that the word at PSTWRK5 contained a log block sequence
  number (BSN).  This did not allow for the first call to PGLOGCNT
  at which point PGLOGCNT has been cleared.  The effect was that
  PGLOGCNT would not save any log tokens once the log BSN passed
  7FFFFFFF.  At this point, DFSDBH30 would cease ensuring that
  DB updates were logged prior to updating the DB.
  
  There was also an error in comparing the passed token against
  the hardened data boundary.  The following conditions had to
  be met.
  - The BSN of the boundary equaled that of the passed token
  - No other token in the OSAM buffers under consideration was
    for a BSN later than the boundary BSN
  Under these conditions, DFSDBH30 might not cause log data for
  DB updates to be written ahead of updating the DBs.
  

Problem conclusion

• GEN:
  KEYWORDS:
  
  *** END IMS KEYWORDS ***
  PGLOGCNT has been rewritten.  It no longer attempts to construct
  BSNs from the log tokens.  Instead, it generates the boundary
  values of uncommitted log data in token format, thus avoiding
  any need to distinguish a BSN of zero from an uninitialized
  BSN field.
  

Temporary fix

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

Comments

APAR Information

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

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

  UI12243

Modules/Macros

•    DFSDBH30
  

Fix information

• Fixed component name

  IMS V13

• Fixed component ID

  5635A0400

Applicable component levels