Re: Help Isolating Data Access

From: William Ryan eMVP (dotnetguru_at_comcast.nospam.net)
Date: 06/11/04 

Date: Thu, 10 Jun 2004 22:31:17 -0400

Chris:

Do you mean the record on the DB side or locally? If you mean on the db,
I'm not sure I understand. Let's say that I have record with a field called
CustNumber and process one with user Bill is accessing it. I pull the
record down into a dataset. During the select I mark the record as Used to
that the same query run now won't return the record b/c the where clause
specifies "where UsageFlag <> '1'" or whatever you do for indicating used.
Is this the scenario? Or do you mean you have 3 or four processes running
locally? If it's locally than you can sync lock the datatable (or the row)
and be done with it (well, that may be an overstatement, I don't want to
overgeneralize when we're talking about threading). 

-- 
W.G. Ryan MVP Windows - Embedded
http://forums.devbuzz.com
http://www.knowdotnet.com/dataaccess.html
http://www.msmvps.com/williamryan/
"Chris Gallucci" <chris@gallucci.com> wrote in message
news:eZfkGjyTEHA.2416@TK2MSFTNGP12.phx.gbl...
> I need help with what I think may be a design issue.
>
> I need to access a record for processing. I need to do it in such a
fashion that several concurrent processes do not access the same
> record.
>
> I've set up a stored procedure that first queries the table for a record
to process than marks the record so that it is now
> unavailable.
>
> The process that executes this stored procedure runs on multiple threads
on multiple machines.
>
> My problem is that I have occasions where two or more threads access the
same record at the same time which causes unwanted
> redundant processing. IOW, I need to be able to guarantee that a record
will never be processed by more than a single thread of
> execution.
>
> Does anyone have a solution or suggestion? Is there a design pattern for
this?
>
> FWIW, the parent process is a Windows Service written in C#.NET (v1.1)
running against a SQL Server 2000 database.
>
> ChrisG
>
>
>

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