At what point oracle write "Checkpoint not complete" in alert log ?

DB version: 10.2.0.4/RHEL 5.8
During a batch run, we encountered lots of 'Checkpoint not complete' errors in alert log.
Later we discovered that ORLs were sized only 50mb and this DB had only 3 redo log group. Since this is the potential cause, we are going create at least 10 Redo log groups and increase Redo log size to 500MB.
But , I want to know what exactly causes oracle to write "Checkpoint not complete" in alert log ?
For the purpose of this discussion, I am assuming we have only 1 ORL per redo log group. Is my below assumption correct ?
ORL1
|----------------> ORL1 file got full, so, LGWR starts writing to ORL2 file. Checkpoint occurs at log switch
| DBWR writes modified blocks associated with the redo entries in ORL1 to datafiles
|
V
ORL2
|----------------> ORL2 file got full, LGWR wants to start writing to ORL3 file. Checkpoint is initiated at log switch.
| But checkpoint can't be finished due to unknowN reasons
|
V
ORL3
|---------------->

Your assumption is only partly right.
I would illustrate it like
ORL1
|
|----------------> ORL1 file got full, so, LGWR starts writing to ORL2 file. Checkpoint occurs at log switch
|                    DBWR starts writing modified blocks associated with the redo entries in ORL1 to datafiles
|
V
ORL2
|----------------> ORL2 file got full, LGWR starts writing to ORL3 file.
|                    Checkpoint for ORL2 is initiated at log switch.
|
V
ORL3
|
|----------------> ORL3 file (the last member) also got full very quickly . LGWR wants to start the 'new cycle' by
                    writing (Reusing) to ORL1. But the checkpoint intiated by the log switch of ORL1 from the previous cycle is
                    not complete yet !! .
Basically you get this error when LGWR attempts to reuse an online redo log file (ORL1 in the above example) and finds that it cannot.
This is because the remaining ORL files (ORL2 and ORL3) got fully written before DB writer finished checkpointing the modified blocks associated with ORL1 yet.
Until the checkpoint of ORL1 is complete, the DB effectively hangs and user sessions have to wait until LGWR can safely reuse ORL1
Yes a larger redo log size of 10 groups can help. But make sure the I/O subsytem where ORLs are stored has no latency issues.

Similar Messages

Checkpoint not complete in alert log file Oracle 11gR2 RAC

Hi,
I found checkpoint not complete in alert log file, almost every 3 seconds .
In metalink i saw for this error, archive_lag_target=0, already this value was set to 0 in my database.
We have 7 redo log groups for each instance, each group is of two redo log files, each file size is 50m.
To avoid this error what i need to do..........
please help me..................

When you "checkpoint not complete" messages in your alert log this normally means your online redo logs are defined too small to handle the load and you have filled and need to switch to a new online redo log before the checkpoint triggered by the previous log switch has been completed.
Increasing your online redo log size is normally the fix for this.
HTH -- Mark D Powell --
PS - The following Oracle support document may also apply:
Checkpoint Not Complete In Alert.log Due To Setting Of Archive_lag_target [ID 435780.1]
Edited by: Mark D Powell on Nov 7, 2011 8:29 AM

"checkpoint not complete" in alert log file.

Hi, all.
I have got a message of "Checkpoint not complete" in alert log file.
Thread 2 advanced to log sequence 531
Current log# 7 seq# 531 mem# 0: \\.\REDO231
Current log# 7 seq# 531 mem# 1: \\.\REDO232
Thread 2 cannot allocate new log, sequence 532
Checkpoint not complete
Current log# 7 seq# 531 mem# 0: \\.\REDO231
Current log# 7 seq# 531 mem# 1: \\.\REDO232
I searched "Checkpoint not complete" issue in this forum.
As solutions,
1. add more redo log groups
2. increase the size of redo log
3. check I/O contention
4. set LOG_CHECKPOINT_INTERVAL, LOG_CHECKPOINT_TIMEOUT or
FAST_START_MTTR_TARGET
I think No.4 is the possible first approach in our environment.
I think No.1 and No2 are not the ploblems in our environment.
I ask the above issue oracle support center, but
I was told that "if you are not getting this message frequently, you do not need to worry about it" from an oracle engineer.
Is this true?? If I am not getting this message frequently, there is no problem
in terms of database integrity, consistency, and performance?
I will be waiting for your advice and experience in real life.
Thanks and Regards.

Redo Log Tuning Advisory and Automatic Checkpoint Tuning are new features introduced in Oracle 10G, if you are on 10g you may benefit from these features.
The size of the redo log files can influence performance, because the behavior of the database writer and archiver processes depend on the redo log sizes. Generally, larger redo log files provide better performance, however it must balanced out with the expected recovery time. Undersized log files increase checkpoint activity and increase CPU usage. As rule of thumb switching logs at most once every fifteen minutes.
Checkpoint frequency is affected by several factors, including log file size and the setting of the FAST_START_MTTR_TARGET initialization parameter. If the FAST_START_MTTR_TARGET parameter is set to limit the instance recovery time, Oracle automatically tries to checkpoint as frequently as necessary. Under this condition, the size of the log files should be large enough to avoid additional checkpointing due to under sized log files.
The redo logfile sizing advisory is specified by column optimal_logfile_size of v$instance_recovery. This feature require setting the parameter "fast_start_mttr_target" for the advisory to take effect and populate the column optimal_logfile_size.
Also you can obtain redo sizing advice on the Redo Log Groups page of Oracle Enterprise Manager Database Control.
To enable automatic checkpoint tuning, unset FAST_START_MTTR_TARGET or set it to a nonzero value(This is measured in seconds and by default, this feature is not enabled, because FAST_START_MTTR_TARGET has a default value of 0). If you set this parameter to zero this feature will be disabled. When you enable fast-start checkpointing, remove or disable(set to 0) the following initialization parameters:
- LOG_CHECKPOINT_INTERVAL
- LOG_CHECKPOINT_TIMEOUT
- FAST_START_IO_TARGET
Enabling fast-start checkpointing can be done statically using the initialization files or dynamically using -
SQL> alter system set FAST_START_MTTR_TARGET=10;
Best regards.

Checkpoint Not complete in alert log

Hello Gurus,
Alert log keeps displaying the following message:
Current log# 3 seq# 80148 mem# 0: /UBSUNDO/ghadb_redo03b.log
Current log# 3 seq# 80148 mem# 1: /UBSTEMP/ghadb_redo03a.log
Thu Dec 06 01:33:20 GMT 2012
Thread 1 advanced to log sequence 80149 (LGWR switch)
Current log# 1 seq# 80149 mem# 0: /UBSUNDO/ghadb_redo01b.log
Current log# 1 seq# 80149 mem# 1: /UBSTEMP/ghadb_redo01a.log
Thu Dec 06 01:34:06 GMT 2012
Thread 1 cannot allocate new log, sequence 80150
Checkpoint not complete
Current log# 1 seq# 80149 mem# 0: /UBSUNDO/ghadb_redo01b.log
Current log# 1 seq# 80149 mem# 1: /UBSTEMP/ghadb_redo01a.log
Thu Dec 06 01:34:14 GMT 2012
Thread 1 advanced to log sequence 80150 (LGWR switch)
Current log# 2 seq# 80150 mem# 0: /UBSUNDO/ghadb_redo02b.log
Current log# 2 seq# 80150 mem# 1: /UBSTEMP/ghadb_redo02a.log
Kindly advice on how to resolve this issue. Database is up for now but i donot want to bounce DB because of this archiving problem.
Thank you.

PVOWUSU wrote:
Hello Gurus,
Alert log keeps displaying the following message:
Current log# 3 seq# 80148 mem# 0: /UBSUNDO/ghadb_redo03b.log
Current log# 3 seq# 80148 mem# 1: /UBSTEMP/ghadb_redo03a.log
Thu Dec 06 01:33:20 GMT 2012
Thread 1 advanced to log sequence 80149 (LGWR switch)
Current log# 1 seq# 80149 mem# 0: /UBSUNDO/ghadb_redo01b.log
Current log# 1 seq# 80149 mem# 1: /UBSTEMP/ghadb_redo01a.log
Thu Dec 06 01:34:06 GMT 2012
Thread 1 cannot allocate new log, sequence 80150
Checkpoint not complete
Current log# 1 seq# 80149 mem# 0: /UBSUNDO/ghadb_redo01b.log
Current log# 1 seq# 80149 mem# 1: /UBSTEMP/ghadb_redo01a.log
Thu Dec 06 01:34:14 GMT 2012
Thread 1 advanced to log sequence 80150 (LGWR switch)
Current log# 2 seq# 80150 mem# 0: /UBSUNDO/ghadb_redo02b.log
Current log# 2 seq# 80150 mem# 1: /UBSTEMP/ghadb_redo02a.log
Kindly advice on how to resolve this issue. Database is up for now but i donot want to bounce DB because of this archiving problem.
Thank you.Those lines are just informational.
no error exists

Oracle 10G Checkpoint not complete Cannot allocate new log

We have an oracle 10G database that has 4 groups of 200M redo logs. We are constantly seeing Checkpoint not complete followed by Cannot allocate new log.. messages in the alert log. When I look at the v$instance_recovery table I see this:
SQL> select WRITES_MTTR, WRITES_LOGFILE_SIZE, WRITES_LOG_CHECKPOINT_SETTINGS, WRITES_OTHER_SETTINGS,
2 WRITES_AUTOTUNE, WRITES_FULL_THREAD_CKPT from v$instance_recovery;
WRITES_MTTR WRITES_LOGFILE_SIZE WRITES_LOG_CHECKPOINT_SETTINGS
WRITES_OTHER_SETTINGS WRITES_AUTOTUNE WRITES_FULL_THREAD_CKPT
0 0 66329842
0 309461 41004
It seems most of our checkpointing is being caused by the log_checkpoint_interval being set to 10000, which means we are doing 20 checkpoints during one redo log since our OS blocksize is 1024. What I'm thinking about doing is first adding two more redo log groups, and then either increasing the log_checkpoint_interval to 40000 (5 checkpoints for one redo log) or unsetting log_checkpoint_interval and setting fast_start_mttr_target to 600. Which would be the recommended parameter change? I think Oracle recommends using the fast_start_mttr_target. Are there any other suggestions?

Hi
>>unsetting log_checkpoint_interval and setting fast_start_mttr_target to 600.
its a better idea,look on it
http://download-uk.oracle.com/docs/cd/B19306_01/server.102/b14237/initparams068.htm#REFRN10058
Just set fast_start_mttr_target parameter.it will resolve ur problem.
Thanks
Kuljeet

Checkpoint not complete error in alert log

version : 10.2.0.5 , 11.2.0.2
This is what I found about "Checkpoint not complete" from google
"+This message indicates that Oracle wants to reuse a redo log file, but the current checkpoint position is still in that log. In this case, Oracle must+
+wait until the checkpoint position passes that log. Because the incremental checkpoint target never lags the current log tail by more than 90%+
+of the smallest log file size, this situation may be encountered if DBWR writes too slowly, or if a log switch happens before the log is completely full,+
+or if log file sizes are too small.+ "
Question1.
What do they mean by Oracle reusing a redo log file ? When one ORL is full , oracle will switch to the next one ; it won't reuse it. Right ?
Question2.
"the current checkpoint position is still in that log" . What is checkpoint position ?
Question3. How often does a checkpoint occur ? (frequency as per time)

Question1.
What do they mean by Oracle reusing a redo log file ? When one ORL is full , oracle will switch to the next one ; it won't reuse it. Right ?You have some groups of redo log, each redo log has members with same information. Redo log run in a circular way, when a group is full, changes to the next group of redo log and when the last group is written continue overwritten the first group.
http://docs.oracle.com/cd/B28359_01/server.111/b28310/onlineredo001.htm
Question2.
"the current checkpoint position is still in that log" . What is checkpoint position ?copy and paste from:
http://docs.oracle.com/cd/E14072_01/server.112/e10713/startup.htm#BABGDACG
"A data structure that indicates the checkpoint position, which is the SCN in the redo stream where instance recovery must begin"
Question3. How often does a checkpoint occur ? (frequency as per time)Checkpoints occur in diferents situations, not per time, please check:
http://docs.oracle.com/cd/E11882_01/server.112/e16508/startup.htm#CNCPT89045

Cannot allocate new log, sequence Checkpoint not complete

Hi,
Im having very frequent log switches and Im getting error as
" cannot allocate new log, sequence Checkpoint not complete"
I was having 3 redo log groups with 50 MB each. After I found this error in the alert log; I increased teh number of redo log groups to 6 with 50MB each. Still the issue is not getting resolved.
Please suggest what will be the best solution for this.
Following is a snippet from alertlog.
==================================================
Sun Apr 19 09:14:08 2009
Thread 1 advanced to log sequence 5811
Current log# 2 seq# 5811 mem# 0: /u01/app/oracle/oradata/mview/redo02.log
Thread 1 cannot allocate new log, sequence 5812
Checkpoint not complete
Current log# 2 seq# 5811 mem# 0: /u01/app/oracle/oradata/mview/redo02.log
Sun Apr 19 09:14:18 2009
Thread 1 advanced to log sequence 5812
Current log# 3 seq# 5812 mem# 0: /u01/app/oracle/oradata/mview/redo03.log
Thread 1 cannot allocate new log, sequence 5813
Checkpoint not complete
Current log# 3 seq# 5812 mem# 0: /u01/app/oracle/oradata/mview/redo03.log
Thread 1 advanced to log sequence 5813
Current log# 1 seq# 5813 mem# 0: /u01/app/oracle/oradata/mview/redo01.log
Thread 1 cannot allocate new log, sequence 5814
Checkpoint not complete
Current log# 1 seq# 5813 mem# 0: /u01/app/oracle/oradata/mview/redo01.log
Sun Apr 19 09:14:32 2009
Thread 1 advanced to log sequence 5814
Current log# 2 seq# 5814 mem# 0: /u01/app/oracle/oradata/mview/redo02.log
Thread 1 cannot allocate new log, sequence 5815
Checkpoint not complete
Current log# 2 seq# 5814 mem# 0: /u01/app/oracle/oradata/mview/redo02.log
Thread 1 advanced to log sequence 5815
Current log# 3 seq# 5815 mem# 0: /u01/app/oracle/oradata/mview/redo03.log
Thread 1 cannot allocate new log, sequence 5816
Checkpoint not complete
Current log# 3 seq# 5815 mem# 0: /u01/app/oracle/oradata/mview/redo03.log
Sun Apr 19 09:14:44 2009
=========================================================
Regards
Pratheej

Anand... wrote:
Hi Sir,
Although i too had suggested increasing the redo logfile size, but after going through [http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:69012348056] i was little confused as Tom has mentioned
Another way is to make the log files smaller, hence increasing the frequency with which we checkpoint ---- Can you explain why so.
I was a little surprised when I read that posting - but noticed it was dated May 2000 - when databases were still quite small and less busy. (And Tom suggested 25MB as being "modest" rather than "tiny" - which is probably what many people would call 25MB these days). And May 2000 probably means 8.0 or 8.1 - and the whole log buffer, redo generation, checkpointing technology has changed a lot since then.
Basically, if you hit "checkpoint not complete", you need more online log space so that it's possible during the busiest times to keep generating redo log information while the checkpoint queues are being cleared far enough to allow older log files to be recycled.
You can do this by adding more log files, or by increasing the sizes of the log files you use. Tom's point, I think, was that if you chose the option to add more files and kept them small (or even made them smaller) then the volume of dirty data blocks that you could create while filling a log file would be small, so the database writer wouldn't have to do much work to make each log file available for re-use. (I'm not sure I'd agree with the approach, though - even for 8i - because it could easily lead to an increase in the volume of datablocks written, even if it did bypass the checkpoint issue).
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
http://www.jlcomp.demon.co.uk
"For every expert there is an equal and opposite expert."
Arthur C. Clarke

Thread 1 cannot allocate new log - Checkpoint not complete caused by small

Hello, one of my customers databases (setup by the customer) is running in archivelog mode. We find every day in the archivelog more than 10x the error "...cannot allocate new log - Checkpoint not complete "
The system has theese parameters:
select group#,members,bytes from v$log;
GROUP# MEMBERS BYTES
1 2 8388608
2 2 8388608
3 2 8388608
4 2 8388608
5 2 8388608
6 2 8388608
7 2 8388608
8 2 8388608
9 2 8388608
10 2 8388608
I asked the formder admin, why the redologs has only 8mb size. The answer was: "To find out, when there was big activity in the database. The count of archivelogs are bigger if you has small redologs. If you use some 250m redologs, we cannot see when tha database has big load. But this is important in case of recovery to recover the database to the point in time before the big load was has taken place." ... ???
Okay, if the customer wants to have 8 MB redologs ... I don´t care. But how can i prevent now the error message? The only way for me is to setup more redolog groups. But it would be very confusing to have 50 or 70 groups of redologs.
What can I do else to prevent the error?

what is the log frequency?
logfile size?
can you check fast_start_mttr_target as well
check the following description:
Sometimes, you can see in your alert.log file, the following corresponding
messages:
Thread 1 advanced to log sequence 248
Current log# 2 seq# 248 mem# 0: /prod1/oradata/logs/redologs02.log
Thread 1 cannot allocate new log, sequence 249
Checkpoint not complete
This message indicates that Oracle wants to reuse a redo log file, but
the current checkpoint position is still in that log. In this case, Oracle must
wait until the checkpoint position passes that log. Because the
incremental checkpoint target never lags the current log tail by more than 90%
of the smallest log file size, this situation may be encountered if DBWR writes
too slowly, or if a log switch happens before the log is completely full,
or if log file sizes are too small.
When the database waits on checkpoints,redo generation is stopped until the
log switch is done.
Edited by: CKPT on Jul 19, 2010 7:37 PM

Problem about "Checkpoint not complete"

Dear Friends ,
I got the following error in my database 2 or 3 times a day . The error is :
Current log# 1 seq# 4127 mem# 0: /dbfs/oradata/ababil/redo01.log
Thread 1 cannot allocate new log, sequence 4128
Checkpoint not complete
I am using Oracle 10g database server where each redo log file size is 512 MB , and each of the file contains ONE member .
Our production server is used in a Private BANK .
In this moment How can I resolve this problem ?

Hi,
Girish, I will try to figure out and you tell me the which is best.
Adding the Space or Size to the Existing Redo Log File Size, it will be effect the some time slack for performing the
Checkpoint as the Case concern with OP.
While comparing with scenario where we are adding the Extra Redo Log File, where the one extra Check point will increase in Cycle and as with respective need size/ space is increased (in terms), but the size of existence file is not changed.
I think better to add an Extra Redo Log File, Instead of increasing the Size of present Redo log file.
Let me know what you think... and please post your concerns and Suggestions.
- Pavan Kumar N

Thread 1 cannot allocate new log, sequence 714 - Checkpoint not complete

I'm working in a Oracle 10g database, running on RHEL. The alert_*.log file is putting out this type of text for the past few months:
Thread 1 advanced to log sequence 713 (LGWR Switch)
Current log#2 seq# 713 mem# 0: /dbfiles/..../onlinelog/filename.log
Current log #2 ..........
Thread 1 cannot allocate new log, sequence 714
Checkpoint not complete
Any ideas to get me pointed in the right direction is appreciated,
Thank you in advance,
Wes

The immediate fixes Vishal suggests are the standard answer, but there is more to it, as the MOS doc he references shows. Additional questions I would ask:
How long is the delay between the inability to switch and when it actually switches? How many datafiles do you have? What is waiting in the db?
In general, I find making log files sized for the rare massive updates, then using the built-in timeouts to switch every 20 or 30 minutes (depending on management recoverability expectations), helps avoid some of these problems. More specifically, run a statspack or awr (if licensed) report for maybe an hour during heavy times, and see what it thinks the waits are. Tuning is an iterative process, and sometimes different things can cause similar symptoms. Sometimes fixing the biggest problem (which is often poor SQL) can radically change the symptoms observed. Other times you find you have dying hardware, or someone messed up a switch configuration.

Checkpoint not complete after Oracle10g upgrade

OS: AIX 5.3
SAP: R/3 46C, 46D_EXT kernel
DB: 10.2.0.2
After upgrading Oracle from 9.2.0.8 to 10.2.0.2 in four SAP systems, Checkpoint not complete warning messages are detected when running CheckDB in DB13.
"BR0976W Database message alert - level: WARNING, line: 4577, time: 2008-06-23 00.25.21, message: Checkpoint not complete"
What I have done after reading OSS 1068186 & 79341 is - Set "_DISABLE_SELFTUNE_CHECKPOINTING" = TRUE ---> This seems to reduce the number of message but doesn't eliminate the issue.
The next step is probably to increase the size of the redo log files. Just wonder if anyone has any clue on this warning and how to resolve it?
Points will be given for helpful tips and information.
Thanks,
Annie

Hi Michael,
I got this in our development system. I don't think it is I/O bottleneck problem. I will increase the DBWR to 2 and see how it goes.
Thanks for the helpful information. I will grant points after work done.
EVENT                          TOTAL_WAITS TIME_WAITED     AVG_MS    PERCENT
db file sequential read            1162987      244978       2.11         68
CPU                                              81609                    23
log file sync                        66074       21198       3.21          6
db file scattered read                5273        5846      11.09          2
log file switch (checkpoint in          49        2222     453.54          1
log file switch completion              75        1715     228.61          0
read by other session                  925         794       8.59          0
latch: redo writing                     25         715     286.14          0
latch free                              65         517      79.52          0
SQL*Net more data to client         181633         514        .03          0

Checkpoint not complete;;cannot allocate new log ;;; PLZ HELP ME

Hi all,
We are working on Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 on a Redhat Linux Server platform.
We are facing the following problem in the alert.log file :
Wed Aug 22 02:58:57 2007
Thread 1 cannot allocate new log, sequence 43542
Checkpoint not complete
Current log# 1 seq# 43541 mem# 0: /u01/oradata/DB01/redo01.log
Thread 1 advanced to log sequence 43542
Current log# 4 seq# 43542 mem# 0: /u01/oradata/DB01/redo04.log
Current log# 4 seq# 43542 mem# 1: /u01/oraindx/DB01/redo04.log
Wed Aug 22 03:00:00 2007
Thread 1 advanced to log sequence 43543
Current log# 5 seq# 43543 mem# 0: /u01/oradata/DB01/redo05.log
Current log# 5 seq# 43543 mem# 1: /u01/oraindx/DB01/redo05.log
Wed Aug 22 03:01:00 2007
Thread 1 cannot allocate new log, sequence 43544
Checkpoint not complete
Current log# 5 seq# 43543 mem# 0: /u01/oradata/DB01/redo05.log
Current log# 5 seq# 43543 mem# 1: /u01/oraindx/DB01/redo05.log
Thread 1 advanced to log sequence 43544
Current log# 6 seq# 43544 mem# 0: /u01/oradata/DB01/redo06.log
Current log# 6 seq# 43544 mem# 1: /u01/oraindx/DB01/redo06.log
Wed Aug 22 03:01:26 2007
Thread 1 advanced to log sequence 43545
Current log# 2 seq# 43545 mem# 0: /u01/oradata/DB01/redo02.log
Thread 1 advanced to log sequence 43546
Current log# 3 seq# 43546 mem# 0: /u01/oradata/DB01/redo03.log
Thread 1 advanced to log sequence 43547
Current log# 1 seq# 43547 mem# 0: /u01/oradata/DB01/redo01.log
Wed Aug 22 03:01:38 2007
Thread 1 cannot allocate new log, sequence 43548
Checkpoint not complete
Current log# 1 seq# 43547 mem# 0: /u01/oradata/DB01/redo01.log
I know that this message indicates that Oracle wants to reuse a redo log file, but
the current checkpoint position is still in that log. In this case, Oracle must
wait until the checkpoint position passes that log. Because the
incremental checkpoint target never lags the current log tail by more than 90%
of the smallest log file size, this situation may be encountered :
1-if DBWR writes too slowly,
or
2-if a log switch happens before the log is completely full,
or
3-if log file sizes are too small.
I read some posts in this forum regarding this error but sincerly i don't know how to find the exact cause of this error? Maybe Should I add new redo files or one new redo group? I don't know how to resolve it :( ;;;
such as I have 6 redo files 3 of them 5MB size and the others 3 files 10MB size ;
Thank you,
Regards,
Message was edited by:
HAGGAR

Make DBWR write more aggressively - as you are on 9i the parameter I would use is FAST_START_MTTR_TARGET=(how long you want recovery to take in seconds), the lower that number, the more aggressively DBWR has to write to keep up with the target, the advantage of this is that by the time LGWR comes to overwrite the redo log file, the chances are that DBWR has already written the "high scn#" (and beyond) from the checkpoint q.
-- This disadvantage is that you will get more I/O to your disks.
2. Create more redo log file groups - this will give DBWR more time to write before LGWR tries to overwrite a particular redolog file, again the chances are that the extra (6th) or (7th) group will give CKPT enough time to completely checkpoint beyond the "highest scn#" before that group is again required..
Which one to go for.. well that's up to you and your setup, if you have an I/O bound system then 2. would be better for you, as 1. will just increase your I/O problem, however if physical space is an issue and I/O isn't then 1. might be better (with the added advantage that instance recovery will also be faster).
Sorry for the training session, but as with everything to do with Oracle, there is rarely one solution that apply to everyone...
Gopu

Thread 1 cannot allocate new log, sequence 1558 Checkpoint not complete

hi,
i m working on oracle 10g rac database on aix machine . i m getting this error on peck time
Thread 1 cannot allocate new log, sequence 1558 Checkpoint not complete
i read lots of documents and they asked to increase size of redo file or add more redo files.
can u plz describe me y m i getting this error ? & how adding redo file can help in this error.
thxs

when yours current redo log filled and then started to switch another log then checkpoint occurs ,this checkpoint started to write dirty buffer from buffer cache to datafile , you cannot reuse this logfile unless checkpoint process writes alls dirty buffer from buffer cache to disk which contained this redo log file.If you attempt to reuse the same log file which cause to checkpoint upon log switch then you will get this error.
Typically this error comes where yours number of redo log switches occuring too frequently or you have less number of redo logs.
lets say if you have 2 redolog file A and B,yours A redolog filled and then oracle switch from redo log A to B,checkpoint occurs,DBWRn started to write dirty buffer to disk meanwhile yours redo log B also get filled antoher log switch occurs to be attempt to reuse redo log file A ,but redo log A will not be entertain unless the previous checpoint completed to write alls dirty block from buffer cache to hard disk which is contained thats redo log A.
Adding redo log will be helpful in this case that redo log will switch to another new added redo log say C and A log file will get more time to be completed checkpoint which he/she contains contents.
Khurram

Chronic checkpoint not complete message in alertlog file

Hi,
We have oracle 10g hosted on linux.i could see the following message in the alert log file.
Thread 1 cannot allocate new log, sequence 184070 Checkpoint not complete.
we have 3 redo log groups with 50MB size.
In the initparameter file:The following values were set.
log_checkpoint_interval = 0
log_checkpoint_timeout =1800
fast_start_mttr_target=0
Can some one guide me what needs to be done to avoid the chronic checkpoint not complete message in the alertlog file.
Thanks

Thank you. Even i listed the history of log switches per hour over the last week:
DAY 00:00 01:00 02:00 03:00 04:00 05:00 06:00 07:00 08:00 09:00 10:00 11:00 12:00 13:00 14:00 15:0
18/08 280 279 283 280 281 283 281 275 279 275 230 0 0 0 0 0 0 0
17/08 279 279 284 281 287 282 282 285 279 279 276 275 278 273 276 277 280
16/08 277 283 283 277 278 279 277 284 279 278 280 280 279 277 280 281 278
15/08 281 281 284 279 279 283 283 284 284 285 282 280 281 282 278 287 276
14/08 272 277 281 278 282 279 279 283 280 281 283 284 283 279 278 278 278
13/08 279 278 281 281 284 285 281 282 270 277 274 275 281 279 280 279 279
12/08 396 403 362 431 430 295 280 281 285 285 280 289 289 284 281 284 279
7 rows selected.

Checkpoint not complete + db_writer_processes/dbwr_io_slaves

Hi,
Oracle Database 11g Release 11.1.0.6.0 - 64bit Production With the Real Application Clusters option.
After I noticed this error into the alert log:
Thread 2 cannot allocate new log, sequence 152831
Checkpoint not complete
Current log# 17 seq# 152830 mem# 0: +ONLINELOG/evodb/onlinelog/group_17.272.729333887
Thread 2 advanced to log sequence 152831
Current log# 14 seq# 152831 mem# 0: +ONLINELOG/evodb/onlinelog/group_14.269.729333871
And read a lot to understand the real cause (for the moment I increased the the redolog file from 5 to 7 (250mb each)).
As it seems I've no problem with the ARCH processes, I read that the cause can be the DBWR0 process that is not "fast" enough to write block I've into redos, and free them for archiving.
I read then something about the asynchronous I/O, and how db_writer_processes/dbwr_io_slaves can simulate the async write to disk.
I think I understood the difference between db_writer_processes and dbwr_io_slaves.
My question is how I can understand if my database needs more DBWR process.
At the moment my configuration is:
db_writer_processes 1
dbwr_io_slaves 0
Thanks in advance,
Samuel

Hi Samuel,
There is still a major confusion on your side concerning the DBWR. It will NOT write data from your redo buffers to the redo logs, since it is the job of the LGWR.
When a log switch occurs (so, you will use a different redo group), then it is the job of the ARCn process(es) to backup the 'used' redo log to a archive log.
When your ARCn process(es) are not fast enough, and a log swicth occurs, it may happen that you have no inactive (read archived) redo group.... then Oracle 'hangs' till it can find such a redo group available.
So, you may want to add 1 (or more) redo group, or increase the size of the redo log files, or have more archiver processes.
DBWr job is to write dirty database blocks back to datafiles.
CKPT also works independently of the LGWR and DBWR.
Check this:
http://www.dbasupport.com/forums/archive/index.php/t-5351.html
And another couple of links:
http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/process.htm
Concepts of checkpoint, dbwr, lgwr processes
HTH,
Thierry
Edited by: Urgent-IT on Feb 10, 2011 5:33 PM
Added mote about CKPT + link
Edited by: Urgent-IT on Feb 10, 2011 5:37 PM
Added another 2 links

At what point oracle write "Checkpoint not complete" in alert log ?

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