Re: Locks Oracle v SQL7

From: Michael Bialik <michael_bialik_at_my-deja.com>
Date: 2000/06/30
Message-ID: <8jhu6r$4l$1@nnrp1.deja.com>#1/1

Hi.

I will try to make it short ( and a bit less precise ): Oracle does NOT put any locks during SELECT. LOCKS are used only for INSERT/UPDATE/DELETE statements.
When some session updates row, the BEFORE-IMAGE of it is written to ROLLBACK SEGMENT. All SELECTing sessions will get the data from that ROLLBACK, so nobody will have to wait for end-user to finish his/her coffe/lunch break and COMMIT the data.
Check "Oracle Concept" documentation for complete description( you can get it on OTN technet.oracle.com ).

HTH. Michael.

In article <gCZ65.5733$uO1.42486_at_news1-hme0>, "Jack" <No_at_Mail.Please> wrote:
> How does Oracle compare with Sql7 as regards Locking problems.
>
> For instance, does Oracle put locks on Select statements, what Locks
does it
> put on Update and Insert statements?
>
> Sql7 puts 'read only' Shared locks on all the above statements
(default
> Isolation mode) but converts the Update and Insert statements (after
> satisfying the Insert and Update conditions) into Exclusive locks in
order
> to do the actual Insert and Update operations. This 'conversion' often
> causes deadlocks.
>
> How about Oracle does it have 'Lock' problems?
>
> Thanks
> J
>
>

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Before you buy. Received on Fri Jun 30 2000 - 00:00:00 CDT