Re: DX Lock problem

From: Charles Hooper <hooperc2000_at_yahoo.com>
Date: Thu, 28 Jun 2007 09:13:59 -0700
Message-ID: <1183047239.892658.77350@w5g2000hsg.googlegroups.com>

On Jun 28, 10:48 am, sorc..._at_gmail.com wrote:
> Hello folks,
>
> does anybody know the meaning of the v$lock.id1 column for a lock of
> type 'DX'?
> We are facing some problems w/ this type of lock.
> Sometimes a session hangs after acquiring a DX lock in exclusive mode
> serializing
> other sessions, any queries againts views related to distributed tx
> ([g]v$global_transaction,
> dba_pending_transactions, ...) hang there forever.
> Killing the session holding the lock doesn't help cause the lock is
> acquired with the same mode
> by another session. The only solution so far has been to shut the
> instance.
> I am trying to replicate the problem in our development environment
> using a couple of
> application witten in Pro*c but even if during some dml operation I
> can see a DX exclsuive
> lock, I havent't been able so far to stall the instance :(.
> If you guys know what excatly means that column, or better if you know
> what Oracle do
> during an distributed (xa) transaction would be greatly valuable for
> my debug activity.
>
> The production env wher i get the error is:
> 9iEE 9.2.0.8 (2 nodes RAC)
> Solaris 9 64
> Bea Web Logic Server 8.1.4 (TM)
>
> Thanks
> g

Google search:
oracle dx lock
or
oracle dx lock commit rollback

Finds this page:
http://www.jlcomp.demon.co.uk/faq/find_dist.html

Quoting:

Whenever a distributed query or DML statement is issued from an instance a Distributed Transaction lock, DX, is taken on the transaction and is visible through v$lock:

	ADDR             KADDR                   SID TY        ID1
	---------------- ---------------- ---------- -- ----------
        070000000015CC48 070000000015CC68         16 DX         29

This entry will remain until the issuer either commits or rollbacks the transaction. This means that a query on a remote object is a transaction and it takes a rollback segment entry to support the twophase commit feature (see References). But while the above query on v $lock will show distributed queries from this instance to a remote database it does not show queries from the remote instance to this instance.

Charles Hooper
IT Manager/Oracle DBA
K&M Machine-Fabricating, Inc. Received on Thu Jun 28 2007 - 11:13:59 CDT