High CPU usage by LMS and Node Evictions: Solved by Setting “_high_priority_processes”

Another thing that may help you in environments with highly interdependent applications:

Our env has high interconnect network block changing, and, as a consequence, high CPU usage by Global Cache Services (GCS)/Lock Manager Server Process (LMS).

This way, for each little latency in the interconnect interface, we were having a node eviction and all the impacts to the legacy application you can imagine (without gridlink or any solution to make the relocation ‘transparent’, as is usual to legacy application) and, of course, the business impact.

Oracle obviously suggested that we reduce the block concurrency over the cluster nodes grouping the application by affinity. But, it’s just no applicable to our env… 🙁

When nothing seemed to help, the workaround came from here: Top 5 Database and/or Instance Performance Issues in RAC Environment (Doc ID 1373500.1).

Here is our change:

boesing@proddb> alter system set "_high_priority_processes"='LMS*|LGWR|VKTM' scope=spfile sid='*';
System altered.

No magic, but the problem stopped to happen. After that, we’re having some warnings about clock synchronization over the cluster nodes on CRS alerts. Like this:

CRS-2409:The clock on host proddb1 is not synchronous with the mean cluster time. No action has been taken as the Cluster Time Synchronization. Service is running in observer mode.

I believe it happens because VKTM lost priority. But it’s OK: The node evictions has stopped! 😀


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