Re:RE: Lock

From: <dgoulet_at_vicr.com>
Date: Tue, 24 Jul 2001 07:32:36 -0700
Message-ID: <F001.00353401.20010724072200@fatcity.com>

A select statement by itself never acquires a lock on the corresponding table(s). In actual practice I have found that no amount of locking has a bearing on a select statement issued from another session. The rule we were all taught in Oracle 4+ about "readers do not block writers and writers do not block readers" is still true.

Now as to "writers blocking writers" that remains a different story. For the most part I totally discourage the use of the "lock table" command among my users and developers. It can cause lock escalation that can get totally out of control and sometimes even cause Oracle to do dead-lock detection with unexpected application failure. I've enough trouble getting our developers to do any kind of robust error detection and handling, never mind them causing an error intentionally.

Now if you want to use the "select .. for update of" that's fine. Otherwise I highly recommend allowing the RDBMS to acquire locks for you as it sees fit. It will acquire the lowest level lock that is consistent with what your trying to do.

Dick Goulet
Oracle Certified 8I DBA
& 16+ year Oracle practioner.

____________________Reply Separator____________________
Author: GL2Z/ INF  DBA BENLATRECHE <kbenlatreche_at_lth.sonatrach.dz>
Date:       7/24/2001 12:35 AM

If I am not wrong you can use a SELECT ........ FOR UPDATE

-----Message d'origine-----

De : Hamid Alavi [mailto:halavi_at_xcare.net] Envoyé : mardi 24 juillet 2001 03:45
A : Multiple recipients of list ORACLE-L Objet : Lock

hi all,

Aay body know, how you can control the lock during the sql code. eg select a,b,c from tablea with NO LOCK. how you can control the locking.

thanks in advance all of you

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