Friday, March 15, 2013

Buffer cache management tip:

New buffer gets are assigned to the head of the LRU (MRU).
But Blocks coming from Full Table Scans are placed to the end of the LRU, and there is a limit for them = db_block_multi_read_count
This method prevents hot blocks to be flushed out from the buffer cache.
This can be thought as default behaviour and can be altered using CACHE clause on table creation or altering. Using Cache clause, blocks coming from an FTS can be placed at the MRU.

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