Usage of Multiple Buffer Pools

Hi, Everyone!

I'm reading "Oracle8i Designing and Tuning for Performance" guide. In chapter "Tuning Memory Allocation"\"Tuning the Buffer Cache" DBA is advised to consider the possibility of Tuning Multiple Buffer Pools.

Now I want to quote an article from the guide:

| A good candidate for a segment to put into the RECYCLE buffer pool is
| a segment that is at least twice the size of the DEFAULT buffer pool and
| has incurred at least a few percent of the total I/Os in the system. A good
| candidate for a segment to put into the KEEP pool is a segment that is
| smaller than 10% of the size of the DEFAULT buffer pool and has
| incurred at least 1% of the total I/Os in the system.
| The trouble with these rules is that it can sometimes be difficult to
| determine the number of I/Os per segment if a tablespace has more than
| one segment. One way to solve this problem is to sample the I/Os that
| occur over a period of time by selecting from V$SESSION_WAIT to
| determine a statistical distribution of I/Os per segment.
| -----
| Oracle8i Designing and Tuning for Performance
| Release 2 (8.1.6)
| Part Number A76992-01

And concerning Tuning Multiple Buffer Pools I have the following questions:

1. How can I sample I/O per segment other than pinging V$SESSION_WAIT? In V$SESSION_WAIT I can capture only current waits and if I/O is taking place at the moment, and save FILE# and BLOCK#. But this means I should ping V$SESSION_WAIT very frequently.
2. A there some other principles for identifying candidate segments for RECYCLE and KEEP pool?
3. Are Multiple Buffer Pools used nowadays? I new about the possibility of using Multiple Buffer Pools at least for 2 year, but never used it or sew other DBA used it.

Thank you!

Sergey Adamenko. Received on Tue May 20 2003 - 03:57:27 CDT