In a RAC environment the buffer cache is global across all instances in the cluster and hence the processing
differs.The most common wait events related to this are gc cr request and gc buffer busy

GC CR request: the time it takes to retrieve the data from the remote cache

Reason: RAC Traffic Using Slow Connection or Inefficient queries (poorly tuned queries will increase the amount of data blocks
requested by an Oracle session. The more blocks requested typically means the more often a block will need to be read from a remote instance via the interconnect.)

GC BUFFER BUSY: It is the time the remote instance locally spends accessing the requested data block.

One Response to “Major RAC Wait Events”

1. Lava Kafle says:

   August 18, 2010 at 12:58 pm

   Simple and beautiful illustration on Global cache and Buffer in Oracle RAC Nodes