Re: Warmth of objects in DB buffer cache?

Hi James,

There is a touch count in X$BH.TCH under release 8.1. I wrote about it in last month's "Ixora News" at http://www.ixora.com.au/newsletter/2000_10.htm#cache. However, it is not incremented for CR buffers, and even hot current buffers can sometimes lose their touch counts. There is also an LRU_FLAG column which is set to 8 for buffers that have been moved to the hot region. One approach is to concentrate on segment header blocks (which are always buffered in current mode) and watch both these columns in X$BH. A handful of samples should be enough to draw reasonable conclusions from.

For more detailed analysis you could use the script "buffers.pl" at http://www.ixora.com.au/scripts/dumps.htm#buffers to print out the file and block numbers of each buffer in LRU order from sample trace files containing 'buffers' dumps.

If you are still working with release 8.0, then you should be able to use X$BH.TEMP which acts as a relative measure of the temperature of the buffer in that release.

@ Regards,
@ Steve Adams
@ http://www.ixora.com.au/
@ http://www.christianity.net.au/

-----Original Message-----
From: jamesdickson_at_my-deja.com

Querying v$bh I know which objects are in my default DB buffer cache at a given point in time. I want to put the most frequently-accessed objects into a new "keep" buffer cache. How can I tell which of the objects are the frequently accessed ones?

The only way I can think of is to query v$bh at regular intervals and see which objects consistently show up there, therefore are not getting aged out. However I would have thought that there would be a statistic to tell me how many times each buffer had been hit since it was originally read from disk - is there any such? Received on Tue Nov 07 2000 - 20:38:35 CST