the ways of buffer hit ratios are mysterious

Greetings, all

 I have some twelve (12) Oracle books, most of them dealing with tuning.

 In all of them, there are discussions about the Buffer Cache Hit Ratio,  with the discussion being, "Thou shalt increase thy DB_BLOCK_BUFFERS in  order to increase thy hit ratio"

 I've reorganized the database, increased DB_BLOCK_BUFFERS,  rebuilt indexes, added indexes, etc, etc, etc. I've gone into the  x$tables, I've set DB_BLOCK_LRU_EXTENDED_STATISTICS to see the  effects of subtracting or adding buffers.

 It seems no matter how much I tweak and tune - some days, the hit  ratio is in the 90's, some days it's in the 70's.

 Since the application is PeopleSoft 6, there's not a lot I can do  to the code.

 It occurred to me that PeopleSoft has a lot of little tables that  are used to retrieve data, and that a lot of table scans are being  done - could this be contributing to what I'm seeing with the hit  ratio? Would it be better to cache these small, frequently used  tables?

 Another application I support called Glovia, has _excellent_  performance statistics - but Glovia is _specifically_ written for  Oracle - it has lots of stored procedures and packages, and takes  advantage of Oracle performance enhancements. PeopleSoft's standard  answer is "we want to make everything generic so it can run on  any database". Well, it makes _my_ life more difficult!

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Before you buy. Received on Fri Dec 17 1999 - 11:16:58 CST