Migrating OPS to cache fusion

Oracle Tips by Burleson

Processing with to Cache Fusion

Cache fusion replaces older methods of concurrency that required disk writes and reads between instances. Every time a block had to be written to disk so it could be re-read was called a ping and was a performance hit.

By sharing blocks between caches of multiple instances in a RAC environment through the high speed interconnect and controlling access to the block through cache latches, enqueues and locks, performance is similar to a single instance.

Be careful if you are upgrading from OPS to RAC, cache fusion only works with the default resource control scheme. If GC_FILES_TO_LOCKS is set, the old pre-cache fusion behavior is utilized. In other words, forced disk-writes will be used resulting in pings.

Cache fusion all but eliminates the need for data partitioning that was required in OPS early releases. You see data was partitioned by use such that all of account receivable data was isolated to a set of tablespaces, as was general ledger, and other application subsets. Then the node that processed that data could be relatively assured that pinging would not occur.

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