how can i calculate the buffer write ratio?

[beksalur]

how can i calculate the buffer write ratio of the db buffer pool? is there a sql for it?

Regards.

 

[ThomVF]

Try reading into "MTTR Advisory" in the Performance Tuning Guide:

Mean Time to Recover (MTTR) Advisory

Starting with Oracle9i Release 2 (9.2), MTTR advisory is available to help you evaluate the effect of different MTTR settings on system performance in terms of extra physical writes.

When MTTR advisory is enabled, after the system runs a typical workload for a while, you can query V$MTTR_TARGET_ADVICE, which tells you the ratio of estimated number of cache writes under other MTTR settings to the number of cache writes under the current MTTR. For instance, a ratio of 1.2 indicates 20% more cache writes.

By looking at the different MTTR settings and their corresponding cache write ratio, you can decide which MTTR value fits your recovery and performance needs. V$MTTR_TARGET_ADVICE also gives the ratio on total physical writes, including direct writes, and the ratio on total input and output, including reads.




Thomas V. Flaherty Jr.
Birch Hill Technology Group, Inc.

http://www.birchhillgroup.com

 

[beksalur]

but i cant get any rows after running
SELECT * FROM V$MTTR_TARGET_ADVICE;