Larger DB_BLOCK_BUFFER and Recursive Calls

We recently performed many benchmarks on running Oracle Applications with a 5 Meg and then 16 Meg Buffer Cache. The Peformance improved in all cases, but particularly for long running batch jobs (improvement=50%) and OLTP improvements were 15%. The Hit Ratios showed little difference, both being quite high at around 90%.

Our benchmarks were performed using echo keystrokes from our application which is currently in Production and our overnight reporting jobs.

BSTAT indicated that the largest improvements were in the following parameters

Buffer Busy Waits (Considerably Less for Large CPU)

Free Buffer Inspected  "         "	  "     "
Free Buffer Requested  "....
Free Buffer Scans      "....
Free Buffer Waits      "....
Parse Time CPU         60% Less for Larger CPU
Parse Time Elapsed     "     "    
Recursive Calls        50% Less for Larger CPU


Physical Reads         40% Less for Large CPU

Message Latch          80% Less for Large CPU

Rollback Trans Waits 90% Less for Large CPU

.. TKPROF indicated that a larger Buffer area user LESS yes LESS !!!! CPU.

Has anybody got any comments on these figures.

The ones that interest me are the Parse Time, Message Latch and in particular, the Recursive Calls. I can't see how the buffer cache could effect parse times.

To my knowledge, recursive calls occur because Oracle needs dictionary info (the Dictionary was perfectly tuned) and dynamic extension. (All temp tables, tables, indexes and rollbacks were sized in all circumstances to overcome this problem).

Can anybody enlighten me on cause of less Parse time, what the message latch is and
what other recursive calls occur apart from dictionary & dynamic extension.

please note. The Benchmarks were performed 12 times, and the results were reasonable consistent.

Mark Received on Wed May 05 1993 - 10:43:16 CEST