IDS Forum

Re: Long transaction

Posted By: Fernando Nunes
Date: Friday, 18 November 2011, at 6:27 a.m.

In Response To: Re: Long transaction (Khaled Bentebal)

One side note:
In most systems, the size of the logical logs used means that 70% of it is
really huge.
We all should consider if we really want to allow a transaction that spans
across 70% of the logical log space defined...
Also note, that on current versions these parameters can be changed
dinamically... which means you can have them relatively low and increase
them before any esporadic maintenance that requires a bigger value.

Regards.

On Fri, Nov 18, 2011 at 11:07 AM, Khaled Bentebal <
khaled.bentebal@consult-ix.fr> wrote:

> The answer is YES for SELECTS.
>
> For UPDATES, DELETES, INSERTS, the other sessions can still do work and
> write into the logs if the LTXHWM is reached for the long transaction
> being rolledback and the LTWEHWM has NOT been reached yet; since rolling
> back a transaction consists of a series of CLR records written to the
> transaction log that perform a bunch of undo operations until the BEGIN
> of the transaction is reached. When the LTXEHWM is reached and the long
> transaction has not been terminated, all of the sessions will be blocked
> and the engine will take the rest of the logs free space between LTXEHWM
> and the end of the logs free space to rollback the long transaction in
> question.
>
> Be careful, depeding on the version of the engine you are using, you can
> hung you engine if DYNAMIC_LOGS is not set in the ONCONFIG. Only IBM
> support can help in this case (a restore wihtout logs can also do but
> you loose all of the transactions since the latest backup).
> For previous versions not allowing DYNAMIC_LOGS , LTXHWM and LTXEHWM
> were set by default to 50 and 60% respectively.
> For the latest version allowing dynamic logs (if set), LTXHWM and
> LTXEHWM are set to 70 and 80% respectively.
>
> Cordialement, Regards,
>
> Khaled Bentebal
> Directeur Général - ConsultiX
> Président UGIF - User Group Informix France
> IIUG - Board of Directors
> Tél: 33 (0) 1 39 12 18 00
> Fax: 33 (0) 1 39 12 18 18
> Mobile: 33 (0) 6 07 78 41 97
> Email: khaled.bentebal@consult-ix.fr
> Site Web: www.consult-ix.fr
>
> Le 18/11/11 06:38, CHUAN LU a écrit :
> > Hi,
> >
> > when long transaction being rollback, could others execute SQL select
> that
> > don't write logical log?
> >
> > thanks.
> >
> >
> >
>
> *******************************************************************************
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> >
> >
>
>
>
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>
>

--
Fernando Nunes
Portugal

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

--0016e64c3bc2d9ae3a04b2009d90

Messages In This Thread

• Long transaction
  CHUAN LU -- Friday, 18 November 2011, at 12:38 a.m.
  • Re: Long transaction
    Art Kagel -- Friday, 18 November 2011, at 5:48 a.m.
  • Re: Long transaction
    Khaled Bentebal -- Friday, 18 November 2011, at 6:07 a.m.
    • Re: Long transaction
      Fernando Nunes -- Friday, 18 November 2011, at 6:27 a.m.

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