Re: Redo Logs Question

You want infrequent log switches, because each log switch flushes dirty blocks from the SGA. The tradeoff is that recovery after a crash will be slightly longer.

I would try making the redo log size 1M. 5k every 90 seconds adds up to about 800k in 4 hours (14400 seconds / 90 seconds * 5k = 800k). Anyway, this seems like a nice round number to start with.

Also, set log_checkpoint_interval to a high number (like 999999) so that checkpoints only occur at log switches.
Also, set log_checkpoint_timeout to zero or a high number (like 28800 which forces at checkpoint 8 hours after the last checkpoint).

This site has plenty of links to keep you busy until you get to a tuning class: http://home.earthlink.net/~bmehta/

Jay Hostetter
Oracle DBA
D. & E. Communications
Ephrata, PA USA

>>> tschruefer_at_mail.howard.k12.md.us 12/31/01 10:20AM >>>
Here is the background of the stiuation I am facing.

We are piloting a application that uses a hybred store and forward system to aggregate all of our disparate student data into one central database. Currently there are 20 schools integrated into the system with another 48 to go, those 20 schools hold about half of our 46k student population.

The system allows (requires) student demographics to be entered through a web client, while grades, attendance, health, conduct, etc. are uploaded over night.

The system comes with the redo log file size set to 5k, which when the users in the 20 pilot schools get going causes a log switch about every 90 seconds. In my limited, steep learning curve expereince, this does not seem like a good thing. Add to that, they cancelled the Oracle Tuning class, which I have to wait until the system is in to take now.

So my questions (that the books don't really seem to want to answer):

How frequently should redo log file switches occur?

How large should my redo logs be?

I am guessing the answer to both of these questions is, It Depends. So my question really is, how do I determine what the correct settings for my installation are?

Tom

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com 
-- 
Author: Tom Schruefer
  INET: tschruefer_at_mail.howard.k12.md.us 

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
San Diego, California        -- Public Internet access / Mailing Lists
--------------------------------------------------------------------
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.com
--
Author: Jay Hostetter
  INET: jhostetter_at_decommunications.com

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
San Diego, California        -- Public Internet access / Mailing Lists
--------------------------------------------------------------------
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).