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Webmaster Forum / ASP / Database Access / June 2009Mulitple users accessing same record - how to work out
I am building an application using classic ASP that may be used by multiple users at a time. What are the methods for working this out? For example, if User A opens the application and selects a record, they can be working on the record as it existed when they opened it. But if User B was to open the application, select the same record as was opened by User A and edits and submits the form, then User A is not aware of the changes made. Thanks, Drew > I am building an application using classic ASP that may be used by > multiple users at a time. What are the methods for working this out? [quoted text clipped - 7 lines] > Thanks, > Drew Look in the documentation for the DB you're using for record locking. Some do it automagically. Google it also. Mike > > I am building an application using classic ASP that may be used by > > multiple users at a time. What are the methods for working this out? [quoted text clipped - 11 lines] > automagically. Google it also. > Mike Thanks for the reply, having a term to search will make this easier. Thanks, Drew ASP pages are stateless, so you can't use the usual database record locking mecanisms and even if they were, you couldn't still use them because if you set a lock on a record but the user don't post back his data, that record will remain locked for everyone else (and possibly even for the primary user; depending on the mecanism used for the record locking. When using a web server, you must be very careful if you want to implement any locking mecanism. For example, you could set a flag with a time limit somewhere using a stored procedure to make sure that not two user got the same flag at the same time. Passed that delay, the flag is invalided for anyone else who may want to take it. When the user post back his data, the flag is first checked to see if it's still valid; ie., it has not been granted to someone else because of an expired delay. If necessary, you can add some AJAX code into your HTML page so that the record will get renewed at a regular interval but you must be very careful about that as you never know when an user will simply walk away for an extended period of time. Instead of using a SP for etablishing your own locking flags, you can also use Application.Lock() and Application.UnLock() - see http://www.java2s.com/Code/ASP/Session-Cookie/ApplicationLockandunLockVBnet.htm - but it's not recommended in term of performance.  SignatureSylvain Lafontaine, ing. MVP - Windows Live Platform Email: sylvain2009 sylvainlafontaine com (fill the blanks, no spam please) Independent consultant and remote programming for Access and SQL-Server (French) On Jun 18, 9:09 am, MikeR <nf4lNoS...@pobox.com> wrote: > Joe wrote: > > I am building an application using classic ASP that may be used by [quoted text clipped - 13 lines] > automagically. Google it also. > Mike Thanks for the reply, having a term to search will make this easier. Thanks, Drew Joe wrote on Thu, 18 Jun 2009 05:22:25 -0700 (PDT): > I am building an application using classic ASP that may be used by > multiple users at a time. What are the methods for working this out? > For example, if User A opens the application and selects a record, they > can be working on the record as it existed when they opened it. > But if User B was to open the application, select the same record as > was opened by User A and edits and submits the form, then User A is not > aware of the changes made. > Thanks, > Drew You could create a checksum of the original data and store this as a hidden field in the form so when the user posts the changes back it compares the checksum with the data in the database and if they don't match then you know something else has edited it during the time the user had it open. What you do then is where it could get tricky - the simple solution would be just to tell the user that the changes could not be made because another user has edited the data and send the new data back to the user along with the new checksum which would then allow them to make any further changes and try posting again. Any method that would involved merging or determining if the current user should have their changes override the other user will be a lot more complex to handle. SignatureDan |
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