IDS Forum

Re: RE: Record Locking and Update Statistics

Posted By: Fernando Nunes
Date: Monday, 3 October 2016, at 8:27 p.m.

In Response To: Re: RE: Record Locking and Update Statistics (RAY BURNS)

Not sure exactly what you're asking...
A table scan readas all the used pages in a table. If there are rows being
changed which are not yet committed when the scan goes through the pages
they will have a lock
The behavior depends on the isolation level and lock mode of the reading
session.
A DIRTY READ will ignore the lock and will read the last version of the row
(which is not committed)
A COMMITTED READ wil take the behavior defined in the LOCK MODE:
- NOT WAIT (default) raises an error
- WAIT N will wiat up to N seconds. If the lock is still there after N
seconds it will raise an error
- WAIT will wait forever until the lock is released
A COMMITTED READ LAST COMMITTED wil behave depending on the operation that
caused the lock:
- if it was an INSERT the row is ignored
- If it was a DELETE the row will be considered
- If it was an UPDATE the last commited image of the row is retrived from
the logical logs

Regards

On Thu, Sep 22, 2016 at 9:52 PM, RAY BURNS <ray.burns@velocityglobal.co.nz>
wrote:

> Many thanks for your suggestions. I have a altered all the update stats
> routines and have a process in place to resolve the problem.
>
> However, I created some test programs and tables on another machine to
> attempt
> to duplicate the problem. Unfortunately I can't seem to repeat the error.
>
> I wonder if someone can tell me how the engine handles the locks when a
> table
> scan is performed on table defined with LOCK MODE ROW? I can't find this
> anywhere in the documentation. I've read the locking chapter in the
> Performance guide, the SQLS and the developers handbook redbook.
>
> Ray
>
>
> ************************************************************
> *******************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>

--
Fernando Nunes
Portugal

http://informix-technology.blogspot.com
My email works... but I don't check it frequently...

--94eb2c07e8060d7a43053dff1a55

Messages In This Thread

• Record Locking and Update Statistics
  RAY BURNS -- Sunday, 28 August 2016, at 7:26 p.m.
  • RE: Record Locking and Update Statistics
    Mike Walker -- Sunday, 28 August 2016, at 8:36 p.m.
    • RE: Record Locking and Update Statistics
      John Miller iii -- Monday, 29 August 2016, at 12:29 p.m.
    • Re: RE: Record Locking and Update Statistics
      RAY BURNS -- Tuesday, 20 September 2016, at 4:02 p.m.
      • Re: RE: Record Locking and Update Statistics
        Art Kagel -- Tuesday, 20 September 2016, at 4:17 p.m.
        • Re: RE: Record Locking and Update Statistics
          RAY BURNS -- Tuesday, 20 September 2016, at 4:27 p.m.
          • Re: RE: Record Locking and Update Statistics
            Art Kagel -- Tuesday, 20 September 2016, at 5:50 p.m.
        • Re: RE: Record Locking and Update Statistics
          RAY BURNS -- Thursday, 22 September 2016, at 4:52 p.m.
          • RE: RE: Record Locking and Update Statistics
            Mike Walker -- Monday, 3 October 2016, at 7:15 p.m.
          • Re: RE: Record Locking and Update Statistics
            Fernando Nunes -- Monday, 3 October 2016, at 8:27 p.m.
      • Re: RE: Record Locking and Update Statistics
        Fernando Nunes -- Tuesday, 20 September 2016, at 5:49 p.m.

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