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RE: Locking records in DB2



fixed

Ron,

As a couple of other people have indicated, doing pessimistic record
locking in a web application is a real recipie for nightmares.  Lets say
you are able to lock the record - what if a user opens up a particular
record for editing, you lock the record, they update the record and maybe
you can handle this fine.  What if they don't update the record, and then
they close the browser instead?  Your web server will not get any
indication that they've done so so how do you know to go and unlock the
record, the only way I can think of to do this would be to somehow write
some code that gets executed when the users' session expires (I don't know
if WebSphere lets you do this or not, I've never had the need to).

You're much better remembering in a session variable how the record looked
when you read it.  Then if the user updates it and hits "Submit", re-read
the record and if it is the same as when you read it the first time, go
ahead with the update, if it has changed show them a page saying "Sorry,
someone else changed the record since you viewed it, please try again" or
similar.

HTH,

Nigel Gay,
Computer Patent Annuities.


> I'm trying to make sure that if a user decides they are going to open a
> particular record for edit mode to make changes, that another user can't
> get into that same record and make changes and overwrite each other.
>
> Ron Power
> Programmer
> Information Services
> City Of St. John's, NL
> P.O. Box 908
> St. John's, NL
> A1C 5M2
> 709-576-8132
> rpower@xxxxxxxxxx
> http://www.stjohns.ca/
>
___________________________________________________________________________
> Success is going from failure to failure without a loss of enthusiasm. -
> Sir Winston Churchill
>
>
>
>
> "Walden H. Leverich" <WaldenL@xxxxxxxxxxxxxxx>
> Sent by: java400-l-bounces+rpower=stjohns.ca@xxxxxxxxxxxx
> 2005/10/04 03:29 PM
> Please respond to
> Java Programming on and around the iSeries / AS400
> <java400-l@xxxxxxxxxxxx>
>
>
> To
> "Java Programming on and around the iSeries / AS400"
> <java400-l@xxxxxxxxxxxx>
> cc
>
> Subject
> RE: Locking records in DB2
>
>
>
>
>
>
> >Do you have a better suggestion than the record lock then in a web app?
>
>
> What are you trying to accomplish?
>
> -Walden
>
> ------------
> Walden H Leverich III
> Tech Software
> (516) 627-3800 x11
> WaldenL@xxxxxxxxxxxxxxx
> http://www.TechSoftInc.com
>
> Quiquid latine dictum sit altum viditur.
> (Whatever is said in Latin seems profound.)
>
>
> -----Original Message-----
> From: java400-l-bounces@xxxxxxxxxxxx
> [mailto:java400-l-bounces@xxxxxxxxxxxx] On Behalf Of RPower@xxxxxxxxxx
> Sent: Tuesday, October 04, 2005 1:52 PM
> To: Java Programming on and around the iSeries / AS400
> Subject: RE: Locking records in DB2
>
> Do you have a better suggestion than the record lock then in a web app?
> That's not being sarcastic either, I'm open to suggestions :)
>
> Ron Power
> Programmer
> Information Services
> City Of St. John's, NL
> P.O. Box 908
> St. John's, NL
> A1C 5M2
> 709-576-8132
> rpower@xxxxxxxxxx
> http://www.stjohns.ca/
> ________________________________________________________________________
> ___
> Success is going from failure to failure without a loss of enthusiasm. -
>
> Sir Winston Churchill
>
>
>
>
> "Walden H. Leverich" <WaldenL@xxxxxxxxxxxxxxx>
> Sent by: java400-l-bounces@xxxxxxxxxxxx
> 2005/10/04 03:15 PM
> Please respond to
> Java Programming on and around the iSeries / AS400
> <java400-l@xxxxxxxxxxxx>
>
>
> To
> "Java Programming on and around the iSeries / AS400"
> <java400-l@xxxxxxxxxxxx>
> cc
>
> Subject
> RE: Locking records in DB2
>
>
>
>
>
>
> >Can anyone help me with understanding what I need to do to use Java and
>
> >SQL to put a record lock on a database file on the iSeries?
>
> You WANT to put a record lock on a row? And how long do you intend to
> hold this lock? The suggestion of "...FOR UPDATE" might work w/in the
> servlet or JSP, but once you return to the user there's no guarantee
> that the user will be serviced by the same iSeries job next time.
>
> Holding a record lock on a web app is not something you usually want to
> do. I guess if you really need to do it, the first thing that comes to
> mind is to hold the lock not in the java program, but in a surrogate job
> you launch specifically for this task.
>
> -Walden
>
> ------------
> Walden H Leverich III
> Tech Software
> (516) 627-3800 x11
> WaldenL@xxxxxxxxxxxxxxx
> http://www.TechSoftInc.com
>
> Quiquid latine dictum sit altum viditur.
> (Whatever is said in Latin seems profound.)
>
>
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> This is the Java Programming on and around the iSeries / AS400
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