Migrating OPS to cache fusion
Oracle Tips by Burleson
Processing with to Cache
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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