PQ62736: SHOW LOGPINNED

APAR status

• Closed as program error.

Error description

• A new "undocumented" command is being added to the TSM
  server to help diagnose problems with a "pinned" recovery
  log.  The TSM manuals will not be updated to reflect this
  command, but the command will be supported within the
  context of why this command was created and the limitations
  on this command.  The new command is
  
  SHOW LOGPINNED
  In general there are five reasons why the recovery log is
  pinned.
  
  1 - There is a transaction associated with a session or
  process that is using space in the recovery log and that
  transaction has been processing for some time, and while
  this transaction is processing space in the recovery log
  is being used buy this transaction and other transactions.
  Space used by other transactions that started after this
  transaction has started is still "used space" in the
  recovery log until this log running transaction completes
  even if those other transactions complete.
  
  2 - The logmode is set to rollforward and space can not be
  freed until the next database backup.
  
  3 - A database backup is currently running and there is
  data in the recovery log that the TSM server still needs
  as part of the database backup processing.
  
  4 - There is a dirty page in the database buffer pool that
  needs to get flushed out to disk before the log tail can
  be advanced.
  
  5 - The log tail can not advance until the next checkpoint.
  A checkpoint is something that the server handles
  automatically as space is used in the recovery log.
  
  Some terminology:
  What is a "pinned" recovery log?  A pinned recovery
  log is when the "log tail" can not be moved because
  there is information needed in the recovery log for
  a transaction that is currently processing, for a
  transaction that has completed but has not been flushed
  to disk, for a currently running data base backup, or
  for a possible "roll-forward" operation on a data base
  restore.
  What is the "log tail"?  The log tail is the point in
  the recovery log that contains the oldest record still
  needed by the server.
  What is the "log head"?  The log head is the point that
  the next record will be written to the recovery log.
  When this command is issued the server will determine if one
  of the first four situations exists.  If none of the first
  four situations exist then the server will report that the
  recovery log is not pinned and space will be freed with the
  next checkpoint operation.
  
  If the second, third or fourth situations exist then the
  server will report which one of those conditions is causing
  the space to be pinned in the recovery log.
  
  If the first situation exists then the server will attempt
  to determine which session or process is associated with the
  transaction that is pinning space in the recovery log.  In
  the process of determining this there will be some additional
  information reported that can be useful if the server is
  unable to determine a session or process assocation with that
  transaction.  If the server is able to determine the session
  or transaction it will report the session or process
  number in addition to some other information such as the
  node name or the command issued for the process.
  
  This command is only intended to be run when the recovery log
  is actually pinned, therefore it is not recommended to
  schedule this command to run on a regular basis.  If the
  recovery log is not actually pinned there are some small
  timing windows where incorrect results may get reported.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All TSM users having to diagnose a problem   *
  *                 with a recovery log that fills too fast.     *
  ****************************************************************
  * PROBLEM DESCRIPTION: There is currently no way to determine  *
  *                      the exact cause for space in the        *
  *                      recovery log not being released.        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  A new diagnostic command is being added to the TSM server.
  The command is SHOW LOGPINNED.  See the APAR opening text
  for details on this command.
  

Problem conclusion

• Apply this fix when available to have a new command
  SHOW LOGPINNED to help diagnose problems with a filling
  recovery log.
  

Temporary fix

Comments

APAR Information

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

  IC33830

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

Fix information

• Fixed component name

  TSM FOR OS/390

• Fixed component ID

  5698ISMVS

Applicable component levels

• R510 PSY

     UP