Re: Buffer cache LRU

From: Tim Gorman <tim_at_evdbt.com>
Date: Sun, 03 Jan 2010 13:12:35 -0700
Message-ID: <4B40FA33.30209_at_evdbt.com>

Back in 2004 or so, Craig Shallahamer explained Oracle touch-count mid-point insertion algorithm (quite a bit more involved than mere "least-recently-used"), downloadable at "http://resources.orapub.com/product_p/tc.htm"...

Taral Desai wrote:

Hi All,

Few Doubts regarding oracle buffer cache. Here is the documentation link from 11g R2.

http://download.oracle.com/docs/cd/E11882_01/server.112/e10713/memory.htm#i12483

Which Says

"The database uses a sophisticated algorithm to make buffer access efficient. Pointers to dirty and nondirty buffers exist on the same least recently used (LRU) list, which has a hot end and cold end. A cold buffer is one that has not been recently used. A hot buffer is frequently accessed and has been recently used."

Now, i was under impression that there is a different LRU which is LRUW for write list but this says LRU maintains both cold, dirty, free, hot all pointers.

Can someone please explain this and also i had few question

1. How to you find that particular buffer in hot, cold or dirty ?

2. How to find buffer is in which list LRU or LRUW ?

To find this do we need SGA dump and if yes where to find this information.

--

Thanks & Regards,
Taral Desai
Samuel Goldwyn  - "I'm willing to admit that I may not always be right, but I am never wrong."

-- http://www.freelists.org/webpage/oracle-l Received on Sun Jan 03 2010 - 14:12:35 CST