Info Required about Check Points
Question about how CKPTINTVL interacts with AUTO_CKPTS in IDS 11.10, and why a 7.31 server with CKPTINTVL 300 shows long gaps between checkpoints. Answers: CKPTINTVL sets the time between checkpoints, so the timer restarts after any checkpoint; AUTO_CKPTS only adds extra checkpoints when needed (it is RTO_SERVER_RESTART, not AUTO_CKPTS, that makes CKPTINTVL ignored entirely - Art Kagel conceded this point). On 7.31 there are no automatic checkpoints, and the engine skips a checkpoint when there has been no write activity, explaining the long gaps. The poster said his understanding was now clear.
Auto-generated by DrWatson from the posts below — may be imperfect; read the full thread.
Hello !
IDS 11.10 FC2W1
We have set
CKPTINTVL 300 & AUTO_CKPTS 1
if AUTO_CKPTS is disabled then there will be a checkpoint after every 300
seconds.
i want to know that as AUTO_CKPTS is enabled what will be the effect on
CKPTINTVL,
auto checkpoints will monitor system activity and the checkpoints will be
triggerd as and when required but then what will happen to the CKPTINTVL 300.
suppose a automatic checkpoint is issued by server and 10 sec after this the
CKPTINTVL is due(due to 300 as set by us) then will there me another
checkpoint 10 sec after the automatic checkpoint.
one of the reasons to force a checkpoint using onmode -c is
To free a logical-log file that contains the most recent checkpoint record and
that is backed up but not yet released (onstat -l status of U-B-L or U-B)
What are the possible reasons for a logical log not to be realeased even after
it is backed up. is it an ongoing transaction being recorded in that logicallog
or what else?
sorry if i am not able to explain my query,just want to understand the
checkpoint occurance/happening mechanism.
IDS 7.31 UC3 (test -server is online but with out much of activity)
all the non system databases in BUFFERED mode.
i dont know if auto checkpoints is a feature of IDS 7.31 UC3
but could not found any such parameter configured in onconfig in one of our
old servers.
the CKPTINTVL set is 300 sec (5 min) but when i check in online.log i can see
that there are no checkpoints for a very long time though the CKPTINTVL is set
to 300 sec.
what could be the possible reasons or have i missed some thing.
First, I believe if your system completes an AUTOCKPT 10 seconds prior to the one that CKPTINTVL would have caused, then the next checkpoint would be CKPTINTVL seconds away. CKPTINTVL does not set times that checkpoints would happen, just the amount of time between checkpoints. So if for some reason the system performs a checkpoint before CKPTINTVL expires, then the next checkpoint would just be CKPTINTVL away from the last one. 7.31 does not have AUTOCKPT. However, if you have no system activity on a server, when CKPTINTVL does expire, the server would check to see if a checkpoint needed to occur. If there is no activity (physical or logical logging or any other write activity) then the system will not perform the checkpoint since there is nothing for that checkpoint to do. So on an inactive system, you can see longer amounts of time between checkpoints then CKPTINTVL if no write activity is happening.
If automatic checkpoints are enabled then CHKPTINTVL is ignored completely.
On Tue, Jun 3, 2008 at 9:57 AM, JACQUES RENAUT <jrenaut@us.ibm.com> wrote:
> First, I believe if your system completes an AUTOCKPT 10 seconds prior to
> the
> one that CKPTINTVL would have caused, then the next checkpoint would be
> CKPTINTVL seconds away. CKPTINTVL does not set times that checkpoints would
> happen, just the amount of time between checkpoints. So if for some reason
> the
> system performs a checkpoint before CKPTINTVL expires, then the next
> checkpoint would just be CKPTINTVL away from the last one.
>
> 7.31 does not have AUTOCKPT. However, if you have no system activity on a
> server, when CKPTINTVL does expire, the server would check to see if a
> checkpoint needed to occur. If there is no activity (physical or logical
> logging or any other write activity) then the system will not perform the
> checkpoint since there is nothing for that checkpoint to do. So on an
> inactive
> system, you can see longer amounts of time between checkpoints then
> CKPTINTVL> if no write activity is happening.
>
>
>
>
*******************************************************************************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>
--
Art S. Kagel
Oninit (www.oninit.com)
IIUG Board of Directors (art@iiug.org)
Disclaimer: Please keep in mind that my own opinions are my own opinions and
do not reflect on my employer, Oninit, the IIUG, nor any other organization
with which I am associated either explicitly or implicitly. Neither do
those opinions reflect those of other individuals affiliated with any entity
with which I am affiliated nor those of the entities themselves.
Thank you Mr Jacques ! For IDS 7.31 UC3 i understood the same thing but now the actuall working of IDS is more clear with your explanation. For IDS 11.10 yes ! even i was talking about the checkpoint intervals(time between 2 checkpoints) and NOT the time required for completing the checkpoint activity/event. Now just to make my understanding more clear (pls correct me if i am wrong) If IDS have completed a checkpoint activity (due to CKPTINTVL expire or AUTO_CKPT )Now. and if considering that AUTO_CKPT will not be issued by IDS. then the next CKPT will occur after the CKPTINTVL expire time from Now. Thanking you once again. Regards vikas
Hello Mr Kagel !
>If automatic checkpoints are enabled then CHKPTINTVL is ignored completely.
vikas:/export/home/informix> onstat -c |grep CKPT
CKPTINTVL 300 # Check point interval (in sec), OLTP optimizedAUTO_CKPTS 1 # Monitor critical resources and trigger
vikas:/export/home/informix> onstat -m
IBM Informix Dynamic Server Version 11.10.FC2W1 -- On-Line -- Up 42 days
00:52:40 -- 4613120 Kbytes
Message Log File: /usr/informix/ids-11.10.FC2W1/online.log
14:10:51 Checkpoint Statistics - Avg. Txn Block Time 0.000, # Txns blocked 0,Plog used 0, Llog used 1
14:20:51 Checkpoint Completed: duration was 0 seconds.
14:20:51 Tue Jun 3 - loguniq 701, logpos 0x8ea018, timestamp: 0x91e15417
Interval: 6605
14:20:51 Maximum server connections 52
14:20:51 Checkpoint Statistics - Avg. Txn Block Time 0.000, # Txns blocked 0,
Plog used 47, Llog used 2
14:25:51 Checkpoint Completed: duration was 0 seconds.
14:25:51 Tue Jun 3 - loguniq 701, logpos 0x8ec018, timestamp: 0x91e156ae
Interval: 6606
14:25:51 Maximum server connections 52
14:25:51 Checkpoint Statistics - Avg. Txn Block Time 0.000, # Txns blocked 0,
Plog used 46, Llog used 2
14:30:51 Checkpoint Completed: duration was 0 seconds.
14:30:51 Tue Jun 3 - loguniq 701, logpos 0x91134c, timestamp: 0x91e15d47
Interval: 6607
14:30:51 Maximum server connections 52
14:30:51 Checkpoint Statistics - Avg. Txn Block Time 0.000, # Txns blocked 0,
Plog used 107, Llog used 37
-------------------------------
14:20:51 Checkpoint Completed
14:25:51 Checkpoint Completed
14:30:51 Checkpoint Completed
pls let me know that if these checkpoints are not initiated by CKPTINTVL and
are triggered by AUTO_CKPT.
pls let me know if i have missed some thing.
Thanking you in advance
Regards
vikas
Did you read Scott Ashley's article on the subject? Do you have automatic
checkpoints enabled?
see:
http://www.ibm.com/developerworks/db2/library/techarticle/dm-0703lashley/
Where it states:
When IDS is configured with the RTO_SERVER_RESTART configuration parameter
turned on, IDS looks at past fast recovery performance along with current
transaction activity and automatically triggers a checkpoint in order to
maintain both the RTO_SERVER_RESTART policy and predictable transaction
response times.
The RTO_SERVER_RESTART and CKPTINTVL configuration parameters are mutually
exclusive; only one of these parameters can be active at a time. If the
server is configured with RTO_SERVER_RESTART, CKPTINTVL is ignored.
On Tue, Jun 3, 2008 at 10:46 AM, VIKAS HIVARKAR <vikashivarkar3@gmail.com>
wrote:
> Hello Mr Kagel !
>
> >If automatic checkpoints are enabled then CHKPTINTVL is ignored
> completely.
>
> vikas:/export/home/informix> onstat -c |grep CKPT
>
> CKPTINTVL 300 # Check point interval (in sec), OLTP optimized> AUTO_CKPTS 1 # Monitor critical resources and trigger
>
> vikas:/export/home/informix> onstat -m
>
> IBM Informix Dynamic Server Version 11.10.FC2W1 -- On-Line -- Up 42 days
> 00:52:40 -- 4613120 Kbytes
>
> Message Log File: /usr/informix/ids-11.10.FC2W1/online.log> 14:10:51 Checkpoint Statistics - Avg. Txn Block Time 0.000, # Txns blocked
> 0,
> Plog used 0, Llog used 1
>
> 14:20:51 Checkpoint Completed: duration was 0 seconds.
> 14:20:51 Tue Jun 3 - loguniq 701, logpos 0x8ea018, timestamp: 0x91e15417
> Interval: 6605
>
> 14:20:51 Maximum server connections 52
> 14:20:51 Checkpoint Statistics - Avg. Txn Block Time 0.000, # Txns blocked
> 0,
> Plog used 47, Llog used 2
>
> 14:25:51 Checkpoint Completed: duration was 0 seconds.
> 14:25:51 Tue Jun 3 - loguniq 701, logpos 0x8ec018, timestamp: 0x91e156ae
> Interval: 6606
>
> 14:25:51 Maximum server connections 52
> 14:25:51 Checkpoint Statistics - Avg. Txn Block Time 0.000, # Txns blocked
> 0,
> Plog used 46, Llog used 2
>
> 14:30:51 Checkpoint Completed: duration was 0 seconds.
> 14:30:51 Tue Jun 3 - loguniq 701, logpos 0x91134c, timestamp: 0x91e15d47
> Interval: 6607
>
> 14:30:51 Maximum server connections 52
> 14:30:51 Checkpoint Statistics - Avg. Txn Block Time 0.000, # Txns blocked
> 0,
> Plog used 107, Llog used 37
> -------------------------------
> 14:20:51 Checkpoint Completed
> 14:25:51 Checkpoint Completed
> 14:30:51 Checkpoint Completed
>
> pls let me know that if these checkpoints are not initiated by CKPTINTVL
> and
> are triggered by AUTO_CKPT.
>
> pls let me know if i have missed some thing.
>
> Thanking you in advance
>
> Regards
> vikas
>
>
>
>
*******************************************************************************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>
--
Art S. Kagel
Oninit (www.oninit.com)
IIUG Board of Directors (art@iiug.org)
Disclaimer: Please keep in mind that my own opinions are my own opinions and
do not reflect on my employer, Oninit, the IIUG, nor any other organization
with which I am associated either explicitly or implicitly. Neither do those
opinions reflect those of other individuals affiliated with any entity with
which I am affiliated nor those of the entities themselves.
<If automatic checkpoints are enabled then CHKPTINTVL is ignored completely. That is not correct. Automatic checkpoint only causes your checkpoints to (potentially) occur more frequently then CKPTINTVL in an attempt to ensure that you perform the new 11.x interval checkpoint, and don't have to complete an oldstyle pre 11 blocking checkpoint. I think you are confusing automatic checkpoints with the RTO_SERVER_RESTART and if that is set to anything other then 0, then that causes CKPTINTVL to be completely ignored.
Ah, entirely possible. Art On Tue, Jun 3, 2008 at 10:57 AM, JACQUES RENAUT <jrenaut@us.ibm.com> wrote: > <If automatic checkpoints are enabled then CHKPTINTVL is ignored > completely. > > That is not correct. Automatic checkpoint only causes your checkpoints to > (potentially) occur more frequently then CKPTINTVL in an attempt to ensure > that you perform the new 11.x interval checkpoint, and don't have to > complete > an oldstyle pre 11 blocking checkpoint. > > I think you are confusing automatic checkpoints with the RTO_SERVER_RESTART > and if that is set to anything other then 0, then that causes CKPTINTVL to > be > completely ignored. > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > -- Art S. Kagel Oninit (www.oninit.com) IIUG Board of Directors (art@iiug.org) Disclaimer: Please keep in mind that my own opinions are my own opinions and do not reflect on my employer, Oninit, the IIUG, nor any other organization with which I am associated either explicitly or implicitly. Neither do those opinions reflect those of other individuals affiliated with any entity with which I am affiliated nor those of the entities themselves.
Sorry Mr Kagel :(
Pls ignore my previous reply.
I have checked in all the other servers and found that where ever AUTO_CKPT is
enabled the checkpoint trigerring is decided by IDS and is not according to
CKPTINTVL specified.
Not sure if the IDS was Rebooted on the instance (where i first checked) after
the AUTO_CKPT was enabled hence my observation is not Viable.
Sorry again and Thank your for your great answers.
Regards
vikas
Auto checkpoints are not available in 7.31 (AFAIK)
The reason a checkpoint will not occur at the expiration of the
checkpoint interval, or before, on 7.31 is when these was no activity (
no updates, deletes or inserts ) The engine will not do a checkpoint if
nothing in the database has changed, there is no reason.
George
-----Original Message-----
From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of
VIKAS HIVARKAR
Sent: Tuesday, June 03, 2008 4:47 AM
To: ids@iiug.org
Subject: Info Required about Check Points [12287]
Hello !
IDS 11.10 FC2W1
We have set
CKPTINTVL 300 & AUTO_CKPTS 1
if AUTO_CKPTS is disabled then there will be a checkpoint after every
300
seconds.
i want to know that as AUTO_CKPTS is enabled what will be the effect on
CKPTINTVL,
auto checkpoints will monitor system activity and the checkpoints will
be
triggerd as and when required but then what will happen to the CKPTINTVL
300.
suppose a automatic checkpoint is issued by server and 10 sec after this
the
CKPTINTVL is due(due to 300 as set by us) then will there me another
checkpoint 10 sec after the automatic checkpoint.
one of the reasons to force a checkpoint using onmode -c is
To free a logical-log file that contains the most recent checkpoint
record and
that is backed up but not yet released (onstat -l status of U-B-L or
U-B)
What are the possible reasons for a logical log not to be realeased even
after
it is backed up. is it an ongoing transaction being recorded in that
logicallog
or what else?
sorry if i am not able to explain my query,just want to understand the
checkpoint occurance/happening mechanism.
IDS 7.31 UC3 (test -server is online but with out much of activity)
all the non system databases in BUFFERED mode.
i dont know if auto checkpoints is a feature of IDS 7.31 UC3
but could not found any such parameter configured in onconfig in one of
our
old servers.
the CKPTINTVL set is 300 sec (5 min) but when i check in online.log i
can see
that there are no checkpoints for a very long time though the CKPTINTVL
is set
to 300 sec.
what could be the possible reasons or have i missed some thing.
************************************************************************
*******
Forum Note: Use "Reply" to post a response in the discussion forum.