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Home -> Community -> Mailing Lists -> Oracle-L -> Re: Re:RE: Deadlock
There is a deadlock here - but I confused the issue by making complete garbage of the last phrase. Instead of:
>> both X and Y might end up waiting for A.
I should have said
>> both Y and Z might end up waiting for X
(which is when you won't get the deadlock)
The critical point comes in the previous paragraph though:
>> With a little luck, Y will be waiting for Z
>> and Z will be waiting for Y (i.e. DEADLOCK)
For Oracle 9, I have only introduced the X session to take out one ITL slot from each of the two blocks because Oracle 9 forces a minimum value of 2 entries per ITL.
This really is a deadlock - which will show a deadlock graph with holders in mode 6 and waiters in mode 4. (X and S if I've got the letters right - personally I prefer numbers).
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
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The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
-----Original Message-----
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
Date: 20 December 2002 22:45
>Jonathon,
>
>This produces ITL waits for sessions Y and Z; but this is not
deadlock. The
>deadlock occurs due to a situation where the Session 1 waits for
something
>to finish in Session 2, which in turn waits for Session 1 AND, this
is
>important, Oracle detects it and kills one of them, rolling back the
>changes, making a deadlock detected error. Is this not the true error
>message that occured in the original thread?
>
>In your example, sessions Y and Z will wait indefinitely until X
commits or
>rolls back. This is not going to be detected by Oracle nor killed by
it. So
>you wouldn't see a message DEADLOCK DETECTED in alert log. Therefore
setting
>INITRANS higher is not going to help at all. Rather the application
logic
>should be checked to remove a real locking conflict.
>
>Am I correct, or am I missing something here?
>
>Arup Nanda
>
-- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Jonathan Lewis INET: jonathan_at_jlcomp.demon.co.uk Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Fri Dec 20 2002 - 17:33:44 CST
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