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Home -> Community -> Usenet -> c.d.o.server -> Re: Rollback segment used in exclusive mode : Why ?
Sybrand Bakker a écrit dans le message
<929810132.19678.0.pluto.d4ee154e_at_news.demon.nl>...
>Hi Emmanuel,
>I'm not sure what's happening, so these are my 'hints'
>I can think of two scenarios.
>The first scenario is the use of the set transaction command places an
>exclusive lock on the dictionary record for the rollback segment. Your
>remark about the Lock Manager seems to confirm that, and it is definitely
>something I am going to repeat on Monday. If this is true, I consider that
>as a bug, and you would think Oracle does too.
How could I verify this ?
>The second scenario is your rollback segment config. The parameter
>transactions per rollback segments usually is derived from the sessions (or
>processes) parameter, divided by the number of public rollback segments.
>Probably your rollback segments are private, so that shouldn't be the
>problem. I believe however you need to check on the current value of
>transactions_per_rollback_segments, because if that parameter equals 1 that
>is the explanation of your problem.
I've allready checked this. The parameters are correct and anyway I use private rollback segment. If I wasn't, I couldn't specify the use of one particular rollback segment for one transaction.
>The only other thing, and that probably is unlikely too: as far as I
>understand the rollback segments, any new transaction will use a different
>extent from the previous one. If you have minimal extents (where 2 is the
>absolute minimum), there could also be a situation of no extents being
>available to start the transaction.
First, I think you're wrong : The rollback are used in a continuous way, so a new transaction doesn't jump to the next extent. Anyway the tablespace which hold the rollback and only one rollback (nothing else) is a 50M large one. The rollback segment has 2 extent (mini) of 5Mo each. So this can't be the reason.
>Personally, I would rather refer to v$rollstat to see what is happening,
one
>of the columns is XACT, the number of active transactions.
I'll check this.
E.G.
--------------------->>>> Emmanuel Guyot <<<<-------------------------- 8 Rue des Montées | Phone : [33] (0)2 38 56 42 72 45100 Orléans | Email : emmguyot_at_altavista.net France | ICQ : 6945538 -----------------------------------------------------------------------Home Page : http://perso.wanadoo.fr/emmanuel.guyot/belote
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