Oracle FAQ | Your Portal to the Oracle Knowledge Grid |
Home -> Community -> Mailing Lists -> Oracle-L -> RE: LGWR using lots of CPU time, low CPU usage
So what is discussed in this paper is outdated already....uh! www.sun.com/blueprints/0101/SunOracle.pdf Gosh, time flies ;) Pages 13-14 talk about Oracle Redo Logs.
As a first attempt, I would consider reducing the number of log members (from 20 to 4, or even 3) than removing them altogether. This will be of some help right away. But monitor further and decide if more Groups are needed to help archiver process.
Do not change multiple things at the same time.
Good Luck,
-----Original Message-----
Sent: Tuesday, November 26, 2002 12:00 PM
To: Multiple recipients of list ORACLE-L
We are on 9.2.0.2, Solaris 8 on Sunfire 3800 with 16 GB memory and 128 MB on a hardware-controlled, mirrored RAID5 StorEdge T-3 Array.
Periodically throughout the day the LGWR background process clocks 20+ minutes of CPU time while actual CPU usage is quite low. I ran a statspack report and for a 45-minute period that included the slow LGWR process.
The top 5 timed events in my 45-minute report are:
CPU time 1,295 60.41
db file sequential read 392,516 341 15.91
db file scattered read 70,245 168 7.85
log file sync 26,916 133 6.22
library cache pin 22 59 2.76
(Now that the top 5 is "timed" events, 3 spots almost always include CPU
and the db file reads, so I only get two other events, usually log file
sync, sometimes enqueue or latch free.)
Statspack also shows the log file parallel write had 28,589 timeouts in that 45 minute period--rather typical for us.
I have session_cached_cursors set to 150.
I am considering the following:
Or is there a better option I'm overlooking?
I would appreciate some advise on the best approach to resolve the slow LGWR process, especially your thoughts on option 1.
Thanks,
Debi
Deborah Lorraine, DBA
University of California, Davis
dlorraine_at_ucdavis.edu
-- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Deborah Lorraine INET: debil_at_ucdavis.edu 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-LReceived on Tue Nov 26 2002 - 13:15:04 CST
(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: Deshpande, Kirti INET: kirti.deshpande_at_verizon.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).