Re: how to place a table in memory

<lambu999_at_yahoo.com> wrote in message
news:1108113932.493568.249100_at_g14g2000cwa.googlegroups.com...

>>
>> If the table is actually "small" from Oracle's perspective (less than
> 2% of
>> buffer cache or 20 odd blocks depending on which is greater), then
> the table
>> is assigned the CACHE characteristic regardless, meaning the table is
> not
>> constantly placed on the cold end of the LRU list (but joins the
> partly 1/2
>> way or so down the list)
>>
>> Then if the table is actually accessed constantly, it should be have
> enough
>> life left in the cache to be re-read from memory (although admittedly
> with
>> 8i/9i at least, the touch count algorithm is prejudiced against
> cached
>> tables)
>>
>
> Richard,
>
> Can you please explain what 'constantly' is? Like once 15 seconds?
>

I used the term "constantly" in response to Chuck's use of the term. However of course, it's all rather vague and subjective what actually constitutes a constantly used table (perhaps, it should be used in an OCP question ;)

I guess my implied interpretation is that if a table is accessed before the associated blocks are aged out of memory (remembering that truly small tables are not simply placed at the "far" cold end of the LRU list), then it's accessed "constantly" enough (just as are all index read blocks).

Whether or not it's 15 seconds or whatever time, is of course dependent on the size of the cache and the associated load on the system at the time, and by implication, how well tuned the buffer cache is/are.

I guess what I'm suggesting is that if a table is truly small and truly accessed frequently, then it may not be continually being read from disk.

Cheers

Richard Received on Fri Feb 11 2005 - 07:37:11 CST