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locking of DBVB6 + Access 2003
I have a app that can add record, modify and view report. the app deploy in around 10 peoples PC. but i want only 1 user can enter the add record form at the same time. any locking of the form can be implemented? My thinking way like this: Whenever somebody click the added form, a value recorded down in either registry or a text file; meanwhile it will check if any entry in the registry or text file, if blank can in and do the add else msgbox (xxx uesr is using) any other suggestion? thanks for all expert advise!!! You want the form to lock?
You should look into the CursorType / LockType properties of ADO LockType: http://www.devguru.com/technologies/ado/8658.asp CursorType: http://www.devguru.com/technologies/ado/8651.asp -- Show quoteHide quoteChris Hanscom - Microsoft MVP (VB) Veign's Resource Center http://www.veign.com/vrc_main.asp Veign's Blog http://www.veign.com/blog -- "Katie" <Katie@question> wrote in message news:%23Iz2i19vFHA.1032@TK2MSFTNGP12.phx.gbl... > VB6 + Access 2003 > > I have a app that can add record, modify and view report. > the app deploy in around 10 peoples PC. but i want only 1 user can enter the > add record form at the same time. > > any locking of the form can be implemented? > > My thinking way like this: > Whenever somebody click the added form, a value recorded down in either > registry or a text file; meanwhile it will check if any entry in the > registry or text file, > if blank > can in and do the add > else > msgbox (xxx uesr is using) > > any other suggestion? thanks for all expert advise!!! > > yes i lock the DB with adLockPessimistic already. but seems still not enough
Show quoteHide quote "Veign" <NOSPAMinveign@veign.com> wrote in message news:euvBAd%23vFHA.2960@tk2msftngp13.phx.gbl... > You want the form to lock? > > You should look into the CursorType / LockType properties of ADO > > LockType: > http://www.devguru.com/technologies/ado/8658.asp > > CursorType: > http://www.devguru.com/technologies/ado/8651.asp > > -- > Chris Hanscom - Microsoft MVP (VB) > Veign's Resource Center > http://www.veign.com/vrc_main.asp > Veign's Blog > http://www.veign.com/blog > -- > > > "Katie" <Katie@question> wrote in message > news:%23Iz2i19vFHA.1032@TK2MSFTNGP12.phx.gbl... >> VB6 + Access 2003 >> >> I have a app that can add record, modify and view report. >> the app deploy in around 10 peoples PC. but i want only 1 user can enter > the >> add record form at the same time. >> >> any locking of the form can be implemented? >> >> My thinking way like this: >> Whenever somebody click the added form, a value recorded down in either >> registry or a text file; meanwhile it will check if any entry in the >> registry or text file, >> if blank >> can in and do the add >> else >> msgbox (xxx uesr is using) >> >> any other suggestion? thanks for all expert advise!!! >> >> > > > yes i lock the DB with adLockPessimistic already. but seems still not The DB may have refused to use adLockPessimistic without telling you. It may > enough have chosen to use adLockOptimistic without telling you. This is perfectly fine in ADO. As I said in my earlier email, check LockType property after opening the recordset to see if the DB accepted it, or switched it to something else. No errors are generated when the DB does not support the Lock or Cursor type that you wanted, it's DB specific. Show quoteHide quote "." <a@a> wrote in message news:%23T08XSdwFHA.700@TK2MSFTNGP11.phx.gbl... > yes i lock the DB with adLockPessimistic already. but seems still not > enough > > "Veign" <NOSPAMinveign@veign.com> wrote in message > news:euvBAd%23vFHA.2960@tk2msftngp13.phx.gbl... >> You want the form to lock? >> >> You should look into the CursorType / LockType properties of ADO >> >> LockType: >> http://www.devguru.com/technologies/ado/8658.asp >> >> CursorType: >> http://www.devguru.com/technologies/ado/8651.asp >> >> -- >> Chris Hanscom - Microsoft MVP (VB) >> Veign's Resource Center >> http://www.veign.com/vrc_main.asp >> Veign's Blog >> http://www.veign.com/blog >> -- >> >> >> "Katie" <Katie@question> wrote in message >> news:%23Iz2i19vFHA.1032@TK2MSFTNGP12.phx.gbl... >>> VB6 + Access 2003 >>> >>> I have a app that can add record, modify and view report. >>> the app deploy in around 10 peoples PC. but i want only 1 user can enter >> the >>> add record form at the same time. >>> >>> any locking of the form can be implemented? >>> >>> My thinking way like this: >>> Whenever somebody click the added form, a value recorded down in either >>> registry or a text file; meanwhile it will check if any entry in the >>> registry or text file, >>> if blank >>> can in and do the add >>> else >>> msgbox (xxx uesr is using) >>> >>> any other suggestion? thanks for all expert advise!!! >>> >>> >> >> > > I am going to guess here.
Use adLockPessimistic, however, I am not sure if you can use that with Access. adLockPessimistic is not supported when the CursorLocation property is set to adUseClient. Read the entire Remarks section in LockType Property. You can be sure what type of locking you are using by checking LockType property AFTER you open the recordset. Example: rs.Open sSQL, cn, adOpenKeyset, adLockPessimistic, adCmdText Debug.Print rs.CursorType ' This may not be what you expect. Debug.Print rs.LockType ' Nor this. The provider is free to choose another LockType without generating an error. This is a perfectly normal behavior! The same is true for CursorType Property. This is provider specific. If you get it to work, you would want to unload the form from Form_Load. You can't use Me.Unload or "Unload Me", use the following indirect method instead: Private Const WM_CLOSE = &H10 Private Declare Function PostMessage Lib "user32" Alias "PostMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long Public Sub UnloadForm(ByVal hWnd As Long) PostMessage hWnd, WM_CLOSE, 0&, 0& End Sub Show quoteHide quote "Katie" <Katie@question> wrote in message news:%23Iz2i19vFHA.1032@TK2MSFTNGP12.phx.gbl... > VB6 + Access 2003 > > I have a app that can add record, modify and view report. > the app deploy in around 10 peoples PC. but i want only 1 user can enter > the add record form at the same time. > > any locking of the form can be implemented? > > My thinking way like this: > Whenever somebody click the added form, a value recorded down in either > registry or a text file; meanwhile it will check if any entry in the > registry or text file, > if blank > can in and do the add > else > msgbox (xxx uesr is using) > > any other suggestion? thanks for all expert advise!!! > U can lock the table. And unlock when closing form.
Or make a table with a record with the formname and the user using it. if user is blank u can set the username so all know its in use. Show quoteHide quote "Katie" <Katie@question> schreef in bericht news:%23Iz2i19vFHA.1032@TK2MSFTNGP12.phx.gbl... > VB6 + Access 2003 > > I have a app that can add record, modify and view report. > the app deploy in around 10 peoples PC. but i want only 1 user can enter the > add record form at the same time. > > any locking of the form can be implemented? > > My thinking way like this: > Whenever somebody click the added form, a value recorded down in either > registry or a text file; meanwhile it will check if any entry in the > registry or text file, > if blank > can in and do the add > else > msgbox (xxx uesr is using) > > any other suggestion? thanks for all expert advise!!! > > That method works as long as you provide a means of clearing the locks if
the program (or Windows) crashes while the lock is set. What I sometimes do for apps using a Access database is have an instance that needs exclusive access to a form create an empty file in the same folder as the database and hold it open then if another instance tries to do the same thing it sees the file and tries to delete it, if it fails it knows another user is doing the same exclusive activity. This automatically clears up any spurious "locks" which may be left about. Best Regards Dave O. Show quoteHide quote "Martin" <ML@community.nospam> wrote in message news:eqGnRACwFHA.904@tk2msftngp13.phx.gbl... >U can lock the table. And unlock when closing form. > > Or make a table with a record with the formname and the user using it. > if user is blank u can set the username so all know its in use. > > "Katie" <Katie@question> schreef in bericht > news:%23Iz2i19vFHA.1032@TK2MSFTNGP12.phx.gbl... >> VB6 + Access 2003 >> >> I have a app that can add record, modify and view report. >> the app deploy in around 10 peoples PC. but i want only 1 user can enter > the >> add record form at the same time. >> >> any locking of the form can be implemented? >> >> My thinking way like this: >> Whenever somebody click the added form, a value recorded down in either >> registry or a text file; meanwhile it will check if any entry in the >> registry or text file, >> if blank >> can in and do the add >> else >> msgbox (xxx uesr is using) >> >> any other suggestion? thanks for all expert advise!!! >> >> > >
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"Katie" <Katie@question> wrote in message I'm no expert, but I can advise you on one point.news:%23Iz2i19vFHA.1032@TK2MSFTNGP12.phx.gbl... > VB6 + Access 2003 > > I have a app that can add record, modify and view report. > the app deploy in around 10 peoples PC. but i want only 1 user can enter the > add record form at the same time. > > any locking of the form can be implemented? > > My thinking way like this: > Whenever somebody click the added form, a value recorded down in either > registry or a text file; meanwhile it will check if any entry in the > registry or text file, > if blank > can in and do the add > else > msgbox (xxx uesr is using) > > any other suggestion? thanks for all expert advise!!! > No RDBMS has any inherent means of insuring concurrency. They do go to great lengths at insuring data integrity and avoiding deadlocks. All data integrity mechanisms (locks, cursors, etc) can help to provide a practical illusion of concurrency, but are doomed to fail at some frequency of use. In order to insure concurrency you have to create your own GateKeeper to manage a queue, usually through a separate service (MTS, ActiveX Exe, ...). In order to manage multiple requests for permission to entering the queue you have to create a TicketMaster to dole out tokens. In your case only one app at a time has a token to open. However, I highly advise you not to go there if you don't have to, as anytime you add a 'human' to the process you also add another level of complexity. For example, what happens when the app successfully requests a token, opens an "Add Form", and the user then goes on a coffee break? You will have to add an expiration date to your tokens. You might want to 'rethink' what you are doing and why. hth -ralph 
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