Wednesday, February 27, 2013

Some Additional Background Processes in RAC

In RAC, each instance will have all the BG processes used in stand-alone configuration, plus the additional BG process required specifically for RAC. Each instance has its own SGA. 
Here I'll mention only few of them.


Global Cache Services (LMS)
This Process copy blocks directly from the holding instance's buffer cache and send a READ-CONSISTENT copy of the block to the requesting instance. The number of LMS processes running is driven by the parameter GCS_SERVER_PROCESSES. By default Oracle start 2 LMS processes.

Global Enqueue Service Monitor (LMON)
This Process monitor the entire cluster to manage the Global resource. When a node joins are leave the cluster, it handles the reconfiguration of locks and resources.

Diagnostic Daemon (DIAG)
This Process monitors the health of the instance and capture diagnostic data regarding process failures within instance.

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