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Re: DX Lock problem

From: Charles Hooper <>
Date: Fri, 29 Jun 2007 07:55:28 -0700
Message-ID: <>

On Jun 29, 6:37 am, wrote:
> On Jun 28, 6:13 pm, Charles Hooper <> wrote:
> > On Jun 28, 10:48 am, wrote:
> > Google search:
> > oracle dx lock
> > or
> > oracle dx lock commit rollback
> > Finds this page:
> >
> > Charles Hooper
> > IT Manager/Oracle DBA
> > K&M Machine-Fabricating, Inc.
> Charles,
> that was clear to me... what is not clear is that I
> can't see the point of acquiring an exclusive lock on an
> object (whatever the object is, I smell it might be an
> undo segment) in exclusive mode and serializing all other
> session.
> The symptom is evident in production: once in a while we see
> this exclusive mode lock of type DX, the database slows down
> and every single query (select i mean) not necessarly issued
> from an xa connection against, for example, the gv$global_transaction
> is there forever.
> I am pretty sure is a bug... but I need to reproduce it somehow.
> Yes, the distributed_lock_timeout is exactly 9000, as Mladen
> suggested me, but i can't even force commit or rollback of that
> in doubt transaction because I can't select from dba_pending_trans.
> g

I will have to defer this question to someone who uses distributed transactions more frequently than I. I recall seeing similar DX locks when I experimented with queries in remote databases. Sessions would occasionally hang for no apparent reason. It seems like ghost sessions would also remain connected to the database, long after the calling session was terminated. At the time I located the above article that indicated a COMMIT or ROLLBACK was needed following a SELECT to clear the lock, and it seemed to make perfect sense.

You might want to check the first two links on this search page:

Mladen, thanks for the parameter hint.

Charles Hooper
IT Manager/Oracle DBA
K&M Machine-Fabricating, Inc. Received on Fri Jun 29 2007 - 09:55:28 CDT

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