MUTEXLCKALERT, Mutual Exclusion subsystem ALERT - Lock attempt threshold crossed for region rrrr. Process pppp is in crit cycle cccc.
Run Time Warning: This warning indicates that process attempting to access a critical section lock for rrrr waited longer than the GT.M determined threshold (approximately two minutes) to obtain the critical section lock held by process pppp; the cycle is measure of the frequency of use of the lock.
GT.M produces this warning when:
There is an IO bottleneck that caused GT.M to slow down: GT.M detects that process pppp is currently using the critical section lock.
A process owning a critical section dies (most likely because of a kill -9) and the OS gives its PID to another process. To reclaim the inappropriately held critical section, GT.M first checks whether the process is alive and whether it holds hold the critical section. On finding that the process is alive but does not hold the critical section, GT.M concludes that it is not safe to free the critical section and alerts the operator with this message.
Action: Monitor the system to determine whether there is a process with process id pppp and whether that process is a GT.M process.
Implement a script to get a stack trace for process pppp or take other appropriate action and use the $gtm_procstuckexec environment variable to activate it immediately before the block process sends the MUTEXLCKALERT message.
Identify and terminate process pppp to release the permissions for that resource. If the process is a GT.M process, use a MUPIP STOP to terminate it. If a process of another application, use an appropriate mechanism to stop it.
If this message is due to an IO bottleneck, adopt a strategy that reduces IO. Some of the IO reducing strategies are:
Revisit your database configuration parameters (especially block size, number of global buffers, journal buffers, and so on) to see if you can make improvements.
Create separate region (database) for temporary globals and do not replicate them.
Consider whether a different database access method and journaling strategy could improve throughput while satisfying your operational needs.
For application configurations with large numbers of concurrent processes and/or large process memory footprints, consider placing object code in shared libraries on GT.M editions that support it. This may free system memory which the OS can use for its file system cache, or which you can use to increase the number of global buffers.
![[Important]](../common/images/important.jpg) | |
Do not apply IO reduction strategies all at once. Try them one at a time and always verify/measure the results of each strategy. |
