Oracle FAQ | Your Portal to the Oracle Knowledge Grid |
![]() |
![]() |
Home -> Community -> Usenet -> c.d.o.server -> Re: 2 Buffer Cache Questions
RogBa..._at_gmail.com wrote:
> 1. If you select * from a table, shouldn't that load the whole table
> into the database buffer cache, provided it fits. I have a script
that
> I found that shows me what's in the cache, but I cannot seem to make
> 100% of a tables block fit. I could not seem to find the answer in
the
> concepts manual.
Look up keep and recycle.
http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96524/c08memor.htm#11256
>
> 2. What's does system put in the buffer cache. We notice that after
> starting the db, system will occupy a good chunk of the buffer cache,
> but that will start to decrease as various queries are run and the
data
> begins to fill the cache.
I thought you said you had a script?
Maybe you should show us the script. Oracle does a lot of stuff in the SGA, and unless you are halting the system and looking at all the bytes in memory, I have difficulty believing any script can create a cohesive and correct snapshot. Even Oracle doesn't know, google discussions of delayed block cleanout for an extreme case, but generally for anything you do, Oracle has to figure out if the necessary blocks are in memory, and if they are part of your transactional view or if Oracle has to fix them to look right. Whether it is a good thing to cache or keep an entire table... depends.
It also helps to post basic informational context: http://www.dbaoracle.net/readme-cdos.htm
jg
-- @home.com is bogus. Or, as Tom would say, Why?Received on Tue May 03 2005 - 16:55:57 CDT
![]() |
![]() |