Re:controlfile schema global enqueue lock

From: <dgoulet_at_vicr.com>
Date: Thu, 01 Feb 2001 07:18:05 -0800
Message-ID: <F001.002A7332.20010201063526@fatcity.com>

Joan,

Something is indeed very fishy in London. The first question I would ask is what is creating so much redo generation? 9x250MB = 2.1GB of data changes inside of that hour. One thought may be that the database is still in hot backup mode from a previously disturbed backup. The other is that several users are doing a lot of temporary table creation, but not in the temp space.

What is the size of this database? Where does incoming data come from? Are their a lot of very frequently refreshed snapshots? Do they do a full refresh vs a fast refresh? What is the db_block_buffer hit ratio like? Having a low hit ratio can indicate an excessively busy dbwr writing dirty blocks to disk which can cause lots of check points.

Dick Goulet

____________________Reply Separator____________________
Author: "Joan Hsieh" <Joan.Hsieh_at_mirror-image.com>
Date:       2/1/2001 6:05 AM

Dear Listers,

Our database in London has tremendous cf enque lock. Since I am new here. I checked the parameter found the log_checkpoint_interval set to 3200 and log_checkpoint_timeout set to default (1800 sec). So I suggest to set log_checkpoint_interval to 100000000 and log_checkpoint_timeout to 0. The second thing I found we have average log switch is 6 t0 8 per hour. We have 40 redo logs, each of them is 250m. Our log buffer set to 1m. I believe after we changed the parameter, the control file schema global enqueue lock should be released. But it get worse, we have 98% control file enqueue lock now. I think we have too many log switch (9 per hour now)and suggested to increase the log to 500m, but our principle dba is not convinced, he think log buffer size should play a more important role.

Any ideas,

Joan

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Author: Joan Hsieh
INET: Joan.Hsieh_at_mirror-image.com

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Author:
INET: dgoulet_at_vicr.com

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