IDS Forum

Re: HA Checkpoint Trigger

Posted By: John Miller iii
Date: Tuesday, 17 March 2015, at 6:36 p.m.

In Response To: Re: HA Checkpoint Trigger (MARK SCRANTON)

The trigger of a checkpoint is not always related to if the servers block
or not. The
blocking is generally due to a lack of resources. In your case it is
because the
physical log was short of resources.

There has been some great administrative improvements with the physical
log. To highlight
a few

New dedicated plog space

Expand the physical log

Move the physical log online

1. The Plog Space
This is a new type of space which will allow only the physical log
in it. No other object is allowed to be stored in a plog space.
By default the plog space grow dynamical along with the
physical log. This saves you having to move the plog and
take twice the space.

2. Move the physical log to a new location while the system is running.
This is the
reason why the undocumented way of changing the configuration file and
bouncing
the server no longer works. You do not need to bounce the server, but
rather just
issue the command and the physical log will be moved during your next
checkpoint.

John F. Miller III
STSM, Lead Architect
miller3@us.ibm.com
503-747-1366
IBM Informix Dynamic Server (IDS)

ids-bounces@iiug.org wrote on 03/17/2015 01:35:40 PM:

> From: "MARK SCRANTON" <mark@markscranton.com>
> To: ids@iiug.org
> Date: 03/17/2015 01:36 PM
> Subject: Re: HA Checkpoint Trigger [34836]
> Sent by: ids-bounces@iiug.org
>
> Dave -
>
> Have never encountered HA as a trigger for CKPT, but it sounds like it's
> simply the plog is too small. We raise a "chkpt request" when the plog
hits
> 75% full, but will keep writing pages to the plog. (We must let critical
> sections finish before we start flushing pages - but the ckpt flag
> is up now).
> The plog will wrap/overflow ("physical log overflow has occurred" is the
msg
> in the msg log) or write to disk if PLOG_OVERFLOW_PATH (I think that's
it) is
> set in the onconfig. The engine is simply blocking transactions to avoid
plog
> overflow. Overflow by itself isn't bad - but if the engines dies you'll
get
> stuck in fast recovery coming back up. If PLOG_OVERFLOW_PATH is
> defined, pages
> that were written there will start being returned to the plog, but
> this can be
> VERY slow depending on # of pages written to disk. That's why it's
> recommending increasing it's size. Since there is 1 plog, you can't
increase
> it "on the fly" - the engine has to bounce. AND - if you've been
> around a long
> time, the old approach was to modify PHYSIZE and bounce. As of either 10
or
> 11, that won't work anymore, even though the msg log will report a
changed
> size (saw this just last month). You must use onparams to resize/move it
(at
> least up through 11.7).
>
> Any changes in 12+ in the area anyone?
>
> Thanks -
> Mark
> www.markscranton.com
> mark@markscranton.com
> The Mark Scranton Group
> "All Informix ... all the time."
>
>
>
*******************************************************************************

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

Messages In This Thread

• HA Checkpoint Trigger
  Informix DBA -- Tuesday, 17 March 2015, at 1:57 p.m.
  • Re: HA Checkpoint Trigger
    MARK SCRANTON -- Tuesday, 17 March 2015, at 4:35 p.m.
    • Re: HA Checkpoint Trigger
      John Miller iii -- Tuesday, 17 March 2015, at 6:36 p.m.
      • Re: HA Checkpoint Trigger
        MARK SCRANTON -- Wednesday, 18 March 2015, at 9:45 a.m.
  • RE: HA Checkpoint Trigger
    Mike Walker -- Tuesday, 17 March 2015, at 5:40 p.m.
  • Re: HA Checkpoint Trigger
    Madison Pruet -- Wednesday, 18 March 2015, at 10:01 a.m.

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