RE: Hmmmmm

What you are observing is the concurrency mechanism as implemented in the Oracle rdbms.  I couldn't explain it better in an email so I suggest you get a hold of Expert One-on-one Oracle by Thomas Kyte, chapter 3 on Locking and Concurrency.  Another thought I have is that it looks like you are trying to implement a sequence number.  If the application can tolerate gaps in the numbers then you can use an rdbms-managed sequence number and use NEXTVAL in place of the SELECT FOR UPDATE.

HTH. Tony Aponte

-----Original Message-----

From: Stefan Jakobsson [mailto:stefan_at_areldata.se]

Sent: Friday, January 25, 2002 5:35 AM

To: Multiple recipients of list ORACLE-L

Subject: Hmmmmm

Having a small problem I need some help with...

The problem is trying to lock a row on a parameter table for an application.

The thing we need to do is following:

Read the value in one row. LOCK that row for other users, increase the value

with one

update the row with the new value and release if for access to other users.

We are trying to use the following SQL statement.

SELECT medlnr FROM parametrar FOR UPDATE OF medlnr NOWAIT;

But the thing is that when we try, anyone can head on in and select the same

value

and even make an update of that row...

What am I missing here?

Regards,

Stefan Jakobsson

Programmer

Arel-Data

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Author: Stefan Jakobsson

  INET: stefan_at_areldata.se

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