Re: Buffer cache LRU

From: Tim Gorman <>
Date: Sun, 03 Jan 2010 13:12:35 -0700
Message-ID: <>


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

Taral Desai wrote:
Hi All,

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

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."
-- Received on Sun Jan 03 2010 - 14:12:35 CST

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