IDS Forum

RE: Re: Checkpoint times

Posted By: Marcus Haarmann
Date: Tuesday, 22 May 2007, at 4:09 a.m.

In Response To: Re: Checkpoint times (Keith Simmons)

Keith,

Thanks for your comment.
I am using KAIO and I thought that AIO threads could be reduced to a
minimum in this case ?
I found out that a slow disk array is the problem and brought down the
chunks.
Now we seem to have better performance, checkpoints are done each 900
sec for 4-5 sec.
But I will reduce the checkpoint interval again to 300 sec to have
better transactional security.

Marcus

-----Original Message-----
From: Keith Simmons [mailto:smiley73@googlemail.com]
Sent: Tuesday, May 22, 2007 9:44 AM
To: ids@iiug.org
Subject: Re: Checkpoint times [9210]

On 21/05/07, Marcus Haarmann <marcus.haarmann@midoco.de> wrote:
> Hi,
>
> we encounter enhanced checkpoint times on a production instance.
> I have tried to modify some parameters which results in less
> checkpoints, but still long (at least for our system).
> Actual config is Sun 280R, 4GB Ram, 2 Processors, Solaris 9 (Sparc),
> IDS 10.00FC6.
> Checkpoint interval was set to 60 sec, but this resulted in a (fuzzy,
> but blocking!) checkpoint each minute for about 11-21 sec. (which
> means the server is not reacting for about 25% of the time).
> I have now set checkpoint interval to 900 sec, set buffers to
> 200000/2k, lru_max/min is 1.5/1.0.
> I have increased physical file size to 100000. Physical buffer is
> 1024, LRUS is 32
>
> Now we get (fuzzy, but still blocking, according to onstat output
> (BLOCKED: CKPT)) checkpoints for about 20-30 sec, but only at 15 min
> intervals.
> Maybe the interval is decreasing over the day because of reaching the
> dirty percentage, I will check for that tomorrow.
> This is better of course, but still I want to know what could be the
> reason, I cannot see we write that many data within a minute.
> I have read that in 9.40, the recommended action for increased
> checkpoints (at least for upgraders of 7.x) is to increase the file
> size for logfiles.
> Is this still true for 10.0 ? Actual log size is 20000 (one log per
> hour normally).
>
> Other useful values:
> # Shared Memory Parameters
>
> LOCKS 500000 # Maximum number of locks NUMAIOVPS 1 # Number of IO vps
> PHYSBUFF 1024 # Physical log buffer size (Kbytes) LOGBUFF 128 #
> Logical log buffer size (Kbytes) CLEANERS 32 # Number of buffer
> cleaner processes SHMBASE 0x10a000000 # Shared memory base address
> SHMVIRTSIZE 500000 # initial virtual shared memory segment size SHMADD

> 50000 # Size of new shared memory segments
> (Kbytes)
> SHMTOTAL 0 # Total shared memory (Kbytes).
> 0=>unlimited
> CKPTINTVL 900 # Check point interval (in sec) TXTIMEOUT 0x12c #
> Transaction timeout (in sec) STACKSIZE 256 # Stack size (Kbytes)
>
> Any recommendations ?
>
> Thanks in advance,
>
> Marcus
>
>
>
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>
>
Marcus

Are you using raw disk or file system files. In either case NUMAIOVPS
needs to be at least 4 (currently all your updates to filestsem files
are going through a single process), and in the latter case it needs to
be around the same as the number of dbspaces plus 3.
Fuzzy checkpoints should be somewhere in the region of 0 - 1 second !!
unless you are performing massive amount of table structure changes.
What does disk io and iowait look like during the checkpoint?
Traditional wisdom always stated CLEANERS and LRUS should be the same
and should be a non-multiple of 2 (31, 63, 127 are good).

Keith

Keith

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Forum Note: Use "Reply" to post a response in the discussion forum.

Messages In This Thread

• Checkpoint times
  Marcus Haarmann -- Monday, 21 May 2007, at 5:09 p.m.
  • Re: Checkpoint times
    ART KAGEL, BLOOMBERG/ 731 LEXIN -- Monday, 21 May 2007, at 5:15 p.m.
    • RE: Re: Checkpoint times
      Marcus Haarmann -- Tuesday, 22 May 2007, at 3:35 a.m.
      • RE: Re: Checkpoint times
        ART KAGEL, BLOOMBERG/ 731 LEXIN -- Tuesday, 22 May 2007, at 7:54 a.m.
  • Re: Checkpoint times
    Keith Simmons -- Tuesday, 22 May 2007, at 3:43 a.m.
    • RE: Re: Checkpoint times
      Marcus Haarmann -- Tuesday, 22 May 2007, at 4:09 a.m.
      • Re: Re: Checkpoint times
        Keith Simmons -- Tuesday, 22 May 2007, at 4:59 a.m.
        • Re: Re: Checkpoint times
          TILMAN MODEL-BOSCH -- Wednesday, 23 May 2007, at 4:19 p.m.
          • Re: Re: Checkpoint times
            ART KAGEL, BLOOMBERG/ 731 LEXIN -- Tuesday, 29 May 2007, at 2:36 p.m.
      • RE: Re: Checkpoint times
        Tilman Model-Bosch -- Wednesday, 23 May 2007, at 4:13 p.m.
        • RE: Re: Checkpoint times
          Robert Roussey\(IT\) -- Wednesday, 23 May 2007, at 4:27 p.m.

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