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Understanding the Oracle advisory utilities

Azeem Mohamed has just published an excellent whitepaper on leveraging the Oracle advisory utilities:

http://www.quest-pipelines.com/pipelines/dba/archives/Understanding_9i_Advisories.pdf

Mohamed also had excellent insights into the Oracle dynamic SGA features and the importance of sizing the Oracle data buffers to minimize disk I/O:

“Now buffer cache has new parameters DB_CACHE_SIZE, DB_KEEP_SIZE and DB_RECYCLE_SIZE that replaces the old parameters DB_BLOCK_BUFFERS, BUFFER_POOL_KEEP, BUFER_POOL_RECYCLE, which are still supported, though are not dynamic. DB_nK_CACHE_SIZE parameter is used to handle non-standard block size caches. Parameters for shared and large pool remain unchanged.”

The article has an outstanding overview of Oracle “granules”, a new unit used for monitoring Oracle RAM allocation and he notes its relation to the sga_max_size parameter:

“In order to achieve dynamic memory management, Oracle uses a new unit of memory allocation called “Granule.” Memory is allocated and freed in terms of granules. Granule size is determined by SGA_MAX_SIZE value and is platform dependent. Its size can be determined by the following conditions:

- On most UNIX systems, granule size is 4 MB if SGA_MAX_SIZE is less than 128 MB, otherwise it would be 16 MB

- On Windows, the largest granule size is 8 MB if SGA_MAX_SIZE is greater than 128MB, otherwise it would be 4 MB”