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  • All significant changes related to the data.
  • MQ log structure
    • Log files
      • S0000000.LOG – S9999999.LOG
    • log control file
      • Amqhlctl.lfh
  • Default location of logs
    • UNIX: /var/mqm/log/
    • Windows: C:\Program Files\IBM\WebSphereMQ\log\
  • Creation, updates & deletion of MQ objects
  • All persistent message updates
  • All transaction states
  • Channel activities.
  • Transaction logs are created at the time of QMGR creation

crtmqm –lc -ll –ld –lf –lp –ls

Flags:

• -lc Use circular logging
• -ll Use linear logging
• -ld LogPath
• -lf LogFilePages
• -lp LogPrimaryFiles
• -ls LogSecondaryFiles
  • Primary log files
  • Secondary log files
  • checkpoint
  • Active log files
  • Inactive log files
  • When primary logs are exhausted these secondary log files are created.
  • Secondary log files specified by the –ls parameter of the crtmqm command
Default 2
Minimum 1
Maximum 509 Unix
Maximum 253 Windows
  • Primary + secondary log files
Maximum 511 Unix
Maximum 255 Windows
Minimum 3

Configuring logs

  • UNIX
    • /var/mqm/mqs.ini
    • /var/mqm/qmgrs/QueueManagerName/qm.ini
  • Windows
    • HKEY_LOCAL_MACHINE\SOFTWARE\IBM\MQSeries\CurrentVersion\Configuration\LogDefaults
    • HKEY_LOCAL_MACHINE\SOFTWARE\IBM\MQSeries\CurrentVersion\Configuration\QueueManager\QueueManagerName\Log
  • mqs.ini:
    • LogDefaults:
    • LogPrimaryFiles=3
    • LogSecondaryFiles=2
    • LogFilePages=1024
    • LogType=CIRCULAR
    • LogBufferPages=0
    • LogDefaultPath=/var/mqm/log

Recovery of damaged objects

  • Circular
    • WMQ objects are not written
    • No object recovery is available
  • Linear
    • WebSphereMQ stores media images in logs only if you are using linear logging
    • Media recovery function
      • −rcdmqimg to record media image
      • − rcrmqobj to recover/recreate object from media image

For a persistent msg all the msg data needs to written to logs for recovering during failures.

Number of primary & secondary log files can be changed.

Log file size can’t be changed after qmgr creation.

If the logs are deleted for some reason then QMGR will not come up . We have to start QMGR from cold restart . If there are any messages that are not processed will be lost as the Transaction logs are deleted .

Even if the logs are corrupted then we need to cold restart of QMGR .Look below procedure to bring back the QMGR to running state .

It is so simple just bare a minute to follow below steps

IBM MQ Cold restart

QMGR Recovery when the Disaster happens due to the Disk failures, Server crashes,Server restart without proper stopping QMGR or Human error’s like MQ administrator mistakenly delete QMGR active logs or Corrupted for some reason and unable to start the QMGR due to such failures . During such scenarios QMGR cold start is a very good technique to bring back the MQ from the Disaster failure.

We should verify the QMGR logs ,FFDC logs carefully to conclude the actives logs are corrupted due to any of the above mentioned reasons then only plan for Cold start .Other wise the check the logs for the reason and rectify based on the error . However we are discussing the situation where the active logs are no more or corrupted .

This document helps to understand how to recover qmgr when its active logs are corrupted. Take the backup of Entire /var/mqm/ before doing any changes  It will not take more space .

strmqm PROD.QM1  This will result below error

From the FDC logs/QMGR logs we see below error .

Take a backup copy of the qmgr data, log files any error logs/FDCs/dumps
Backup of /var/mmq/log/

Verify the existing QMGR /var/mqm/qmgrs/PROD.QM1/qm,ini file and take the below values from the QMGR. We will be creating TEMP QMGR with the exact  same attributes . We will not be starting this QMGR .

LogPrimaryFiles=100
LogSecondaryFiles=50
LogFilePages=2048
LogType=CIRCULAR

crtmqm –lc –lf 2048 –lp 100 –ls 50 TEMP

Once the TEMP QMGR is created we will not be starting this . We just need the active logs from /var/mqm/log/TEMP/active and /var/mqm/qmgrs/TEMP/amqalchk.fil file from TEMP QMGR to original QMGR .

/var/mqm/log/TEMP/active/* —> /var/mqm/log/PROD.QM1/active
/var/mqm/qmgrs/TEMP/amqalchk.fil —> /var/mqm/qmgrs/PROD.QM1/

We have replaced corrupted logs with the new logs .
Now start the QMGR with strmqm PROD.QM1
verify the status of QMGR using dspmq
Verify if there are any FDC logs , check the QMGR logs .If all the fine then verify the channel status . If all the channel status are good then we have successfully recovered the QMGR .

Please verify the connectivity with the Applications connecting to this qmgr.
Data in the queues is preserved if messages are persistent.

You can delete TEMP QMGR now . dltmqm TEMP

Hope this give some good insight about the MQ logs and some scenarios where Transaction logs corrupted or missed .

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