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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Cache a table
>From 9.2 doc:
The LRU Algorithm and Full Table Scans
When the user process is performing a full table scan, it reads the blocks
of the table into buffers and puts them on the LRU end (instead of the MRU
end) of the LRU list. This is because a fully scanned table usually is
needed only briefly, so the blocks should be moved out quickly to leave more
frequently used blocks in the cache.
You can control this default behavior of blocks involved in table scans on a table-by-table basis. To specify that blocks of the table are to be placed at the MRU end of the list during a full table scan, use the CACHE clause when creating or altering a table or cluster. You can specify this behavior for small lookup tables or large static historical tables to avoid I/O on subsequent accesses of the table.
Waleed
-----Original Message-----
Sent: Tuesday, October 21, 2003 8:59 AM
To: Multiple recipients of list ORACLE-L
Mike:
I guess we are aware there is no concept of LRU or MRU in current versions of Oracle and I don't think CACHE option will influence the behavior. With the new algorithm the MFU blocks are already in the hot end (unless they are read using CR read in that case they will be in cold end since we set the _db_aging_freeze_cr to TRUE) and we don't need to cache the blocks explicitely.
You can monitor the behavior of this using the X$BH (espicially the last two columns TCH and TIM).
-- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: K Gopalakrishnan INET: kaygopal_at_yahoo.com Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Khedr, Waleed INET: Waleed.Khedr_at_FMR.COM Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Tue Oct 21 2003 - 08:29:39 CDT
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