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Preventing GK Systems standstill due to Leaked lock entries

This page is part of the larger series of blogs relating to SAP Omnichannel POS –  Admin & Operational Topics.

This page discusses about the most prominent logs which occur in the GK Application logs related to Leaked lock entries in the SAP Enqueue Server.

 

Issue classification:

Location of these Logs Severity Immediate Action Needed?
In all GK Cluster applicaiton logs (Info / Debug) Very High Yes. The System may be not processing anything already due to this issue

Example Error snippet:

******************************************************************************************************************************
2018-08-16 01:26:50.047 WARN  {taskExecutor-9} [N/A] [N/A   ] [SapLockMonitoring] !!! There are potentially leaked locks (acquired before more than 30 minutes – lockTimeBorder=Wed Aug 16 00:56:50 UTC 2018)…
2018-08-16 01:26:50.047 WARN  {taskExecutor-9} [N/A] [N/A   ] [SapLockMonitoring] Please check SAP Enqueue monitoring web function for details (SAP NetWeaver Administrator – Troubleshooting/Locks)
2018-08-16 01:26:50.047 WARN  {taskExecutor-9} [N/A] [N/A   ] [SapLockMonitoring]
2018-08-16 01:26:50.047 WARN  {taskExecutor-9} [N/A] [N/A   ] [SapLockMonitoring] Lock list:
2018-08-16 01:26:50.047 WARN  {taskExecutor-9} [N/A] [N/A   ] [SapLockMonitoring]   – LockEntry[user= Guest, owner=U2018080803095097100000…………….376788451, name=SDC                           , argument=PerformanceMonitoringAlerter_NotificationLockObject                                                                                                   , mode=E, count=1]
2018-08-16 01:26:50.048 WARN  {taskExecutor-9} [N/A] [N/A   ] [SapLockMonitoring] ******************************************************************************************************************************

This warning message above clearly indicates that there are some locks in the SAP Enqueue server being held up and possibly the associated Application context / thread is not present.

Root causes could be:

  • The relevant application (in the above example, it is SDC) has either crashed and started on its own, however some locks in the Enqueue Server still remained.
  • The relevant application (in the above example, it is SDC) was restarted intentionally, however some locks in the Enqueue Server still remained.

Checks needed to ascertain:

  • Open NWA tool and check the locks present in the SAP Enqueue Server.
  • Check for old / stale locks matching the description in the logs
  • If they are present and do not have any change in status, etc, then this most likely is a ghost lock.

To Solve this:

  • Always ensure the cardinal rule: If this leaked lock is related to CIS (if the warning message is recorded in CIS logs), then always shutdown all GK Cluster applications first.
    • And then restart CIS.
    • Check from NWA tool that the Ghost (stale) locks are gone. If not Only the COMPLETE NW JAVA system restart can bring the GK Applications back to normal state
  • If the leaked lock is for other GK Cluster applications, then try the following
    • Restart the impacted application alone.
    • Check, if the leaked locks are gone in the NWA tool.
    • If not, only the COMPLETE NW JAVA system restart can bring the GK Applications back to normal state

Impact,  if not acted on

  • Possibly the affected application is already not functioning, depending upon the nature and the type of the lock.
  • Should the Application be in a working condition, then slowly there would be a pile up of threads waiting for this specific lock, and the GK Application as well as the DB connections will be exhausted thus bringing the whole System to a halt.

To Prevent this issue:

  • Always restart the complete NW Java system to avoid this contentious issue.
  • If a single GK Application restart is necessary, then always check the Enqueue Server locks for any stale locks from before the restart of the particular application.

Have a look at the Blog: SAP Omnichannel POS by GK – Admin & Operational topics, for more topics related to SAP Omnichannel POS by GK.

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