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From "Sperlich, Tino" <t.sperl...@hpc-hamburg.de>
Subject AW: Village for Oracle patch.
Date Tue, 02 Nov 2004 11:10:02 GMT
Hi,

I have faced a similar problem lately 
and I think that issue is a general torque one
rather than only blob-related.
With the help of
Arne Siegel I've solved it for my part.
See Arne's comments here:
<http://www.mail-archive.com/torque-user@db.apache.org/msg03288.html>

HTH, regards,

Tino

-----Urspr√ľngliche Nachricht-----
Von: Ben Bookey [mailto:ben.bookey@gistec-online.de]
Gesendet: Dienstag, 2. November 2004 09:55
An: Apache Torque Users List
Cc: saravkrish@uky.edu
Betreff: AW: Village for Oracle patch.




Hi Saravana,


> >>Is this hanging noticed only in tables with LOBs or does it hang on any
> >>table where locking is performed?
>
> This is a very good question :-) I think that this table with the LOB is
the
> only one where any locking is taking place in my application. My
> understanding is that Oracle locking is only done when a specific "select
*
> where * for update" command is used (this command is also system.out'd,
> presumably from your patch). If this is the case, then its the only table
> where I have noticed this problem, as the remainder of the app is doing
> standard Torque Deletes, Updates and Inserts using Torque (varchar and
> numbers) and I believe from the Torque logs that no such commands are
done.

==So I assume you access your tables using only Torque and don't use any
==custom SQL statements to access the database.
Correct.

> One futher point I would like to add, is that this problem is not likely
to
> happen alot in my app. I have locked the row
> using SQLplus, and not another instance of myApp.

==What do you mean by "locked the row using SQLplus"? Do you mean Stored
==procedures? Why do you lock the row in the first place? I'm confused.
==Explain more about the scenario please. What is myApp (I can see its
==something you wrote ;-) ) Is your application a webapp or a standalone
==app?

MyApp is a tomcat, servlet database app with jsp. Upto max 20 users
accessing the same
oracle instance and tablespace using this app. After sleeping on it:-) the
only place
where locking must take place is with the BLOB. This is due to the writing
of the filesize normally
associated with blobs (we limit this to 30k but this can be increased if the
customer so wishes).

In this environment users *could* get conflicts, when attempting a blob
update simultanesously on
the same row. I reproduce a locking scenario by using the
%ORACLE_HOME%\ora92\bin\SQLplus.exe, and selecting for update a particular
row containing a LOB for update. I then attempt a blob update with myAPP and
it hangs until
I COMMIT on SQLplus.exe. This is in affect reproducing a slow update of the
blob to the database.

We are a group of three developers.

==I think there is a way to ask Oracle to not wait (add NO WAIT at the
==end) but I'm not sure I want to make it the default option of Village. I
==don't know if Torque passes on "lock requirements" to Village. If it
==does and I can figure out how to get that property within village, I can
==add the feature to not wait on locks.

Thats what I was thinking. Adding NO WAIT, and returning an Exception, would
remove this problem( issue would be better perhaps:-)) completely.  I guess
I have not really thought about the "real chances" of user-conflicts
occuring in myAPP. I suppose the chances are minimal, and because the
filesize is also minimal a second user shouldnt have to wait so long until
lock is released. More conflicts would occur when the filesizes are bigger.

Await your comment :-)

Ben

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