ОТН.: ОТН.: ОТН.: How to track logfile switch
- From: Yavor Ivanov <Yavor_Ivanov@xxxxxxxx>
- To: "Bort, Guillermo" <guillermo.bort@xxxxxxx>, "Bobak, Mark" <Mark.Bobak@xxxxxxxxxxxx>, oracle-l <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 3 Oct 2008 20:01:40 +0300
Maybe I have to write this again.
The redo log files are 512 MB each. The archivelog files are usually 1-3 MB. So
increasing redo log size will solve nothing. Maybe you are advising larger redo
log buffer, but why?
Making more redo log groups will help. But I still wonder why the switches are
so frequent.
I know DML generates redo. But the redo log files are too far from filling. I
was trying to catch "alter system " using AFTER DDL trigger, but maybe it is
not DDL too. I may try using database auditing, but it will not be easy
(political reasons). So I was just wondering if there is some other way to find
what may cause so strange frequent log switches
Regards,
Yavor Ivanov
________________________________
От: Bort, Guillermo [guillermo.bort@xxxxxxx]
Изпратени: 03 Октомври 2008 г. 19:43
До: Yavor Ivanov; Bobak, Mark; oracle-l
Тема: RE: ОТН.: ОТН.: How to track logfile switch
Alter system are not DML. DML are regular old fashioned SQL such as insert,
update and delete. As someone else said in the list, every DML generates redo
information and when the redo log file becomes full a log switch automatically
occurs. This is basic transaction processing in Oracle. I would go with
increasing the size of redo log buffer and maybe redo log files to have less
than four log switches per hour during normal operation. And take it from
there. I reckon the frequency of the problem will decrease greatly or the
problem may even dissapear.
HTH
Guillermo Alan Bort
EDS - ITO DBA Main Group
From: Yavor Ivanov [mailto:Yavor_Ivanov@xxxxxxxx]
Sent: Friday, October 03, 2008 1:00 PM
To: Bort, Guillermo; Bobak, Mark; oracle-l
Subject: ОТН.: ОТН.: How to track logfile switch
This sound promising. What DML could cause log switch (other than "alter system
switch logfile" and "alter system archive log ...")?
The issue happens during normal daily load.
Regards,
Yavor Ivanov
________________________________
От: Bort, Guillermo [guillermo.bort@xxxxxxx]
Изпратени: 03 Октомври 2008 г. 18:45
До: Yavor Ivanov; Bobak, Mark; oracle-l
Тема: RE: ОТН.: How to track logfile switch
It may be silly to mention this, however log switches can be caused by valid
dml processing not just alter system switch logfile. I’ve found that increasing
redo log size and redo log buffer often helps lower the number of Checkpoint
not Complete. Do you notice this issue during periods of high transaction load
or batch load? Also, do you have fast_start_mttr_target set to a static value?
HTH
Guillermo Alan Bort
EDS - ITO DBA Main Group
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Yavor Ivanov
Sent: Friday, October 03, 2008 12:36 PM
To: Bobak, Mark; oracle-l
Subject: ОТН.: How to track logfile switch
The value of ARCHIVE_LAG_TARGET is 0
Unfortunately the message "Thread X cannot allocate new log, sequence XXXX" is
sometimes followed by "Checkpoint not complete". So I cannot ignore it easily.
Yesterday there was a short but noticeable database hang at the same time when
this happened.
Regards,
Yavor Ivanov
[SNIP]
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