Re: lock Oracle db objects, but only a lock for others?

From: Eric Fortin <emfortin_at_attbi.com>
Date: Mon, 21 Apr 2003 02:00:45 GMT
Message-ID: <hhIoa.546603$3D1.301064@sccrnsc01>

"Daniel Morgan" <damorgan_at_exesolutions.com> wrote in message news:3EA32BBB.1A412583_at_exesolutions.com...
> Eric Fortin wrote:
>
> > "Daniel Morgan" <damorgan_at_exesolutions.com> wrote in message
> > news:3EA31A5F.C26DAB1A_at_exesolutions.com...
> > > > > On Error Goto
> > > >
> > > > What is the correct way to Error Handle in VB6?
> > >
> > > To handle the errors in the back-end, or middle-tier ifone exists: Not
in
> > the
> > > front-end. VB should only be used to display messages returned from
the
> > serer.
> >
> > >
> > > > >
> > > > > If things like this have been written expect that the entire code
base
> > > > needs to
> > > > > be rewritten.
> > > > >
> > > >
> > > > Can you please give an example of a correct construction for VB6 and
> > Oracle?
> > > >
> > > > (or is it the order, begin trans followed by error handling)
> > > > (or is it that vb6 should not be used with Oracle)
> > > >
> > > > I guess I'm not clear on how it should be done.
> > > >
> > > > Thanks.
> > >
> > > No problem. I teach an entire certificate program, three quarters, at
the
> > > University of Washington on the subject. So I'll just include all of
that
> > > information here in this usenet post
> > > (http://www.outreach.washington.edu/extinfo/certprog/oad/oad_crs.asp)
just
> > > kidding. Seriously this is not
> > > something that can be done generically. Just to give you an example of
> > what I
> > > would consider minimal information required to construct Oracle error
> > handling
> > > ... I would say that you must understand all of the following:
> > >
> > > TooManyDays EXCEPTION;
> > > EXCEPTION WHEN TooManyDays THEN
> > > EXCEPTION WHEN NO_DATA_FOUND THEN
> > > EXCEPTION WHEN OTHERS THEN
> > > PRAGMA EXCEPTION_INIT
> > > RAISE;
> > > RAISE_APPLICATION_ERROR(-20001, 'Date Can Not Be In The Future');
> > > AUTONOMOUS TRANSACTIONS
> > >
> > > And likely I'll think of something I missed as soon as press the SEND
> > button.
> > >
> > > Daniel Morgan
> > >
> >
> > On error goto is in the VB6 code
> >
> > if that exception is thrown in the db and not handled in the VB app, the
vb
> > app will get a terminating ora-440 error. (Then, especially if no begin
> > trans, all the sql up to that point will be auto committed and the sql
after
> > that 440 error will never be executed)
> >
> > Here is the Oracle Doco ( bottom of the page): on how to do it with Ora
OLE
> > DB.
> >
> >

(http://download-west.oracle.com/docs/cd/B10501_01/win.920/a95498/using.htm#
> > 1006186)----code sample:Dim Oracon As ADODB.Connection
> > Dim recset As New ADODB.Recordset
> > Dim cmd As New ADODB.Command
> > Dim param1 As New ADODB.Parameter
> > Dim param2 As New ADODB.Parameter
> > Dim objErr As ADODB.Error
> > Dim Message, Title, Default, EmpNoValue
> >
> > Message = "Enter an employee number (5000 - 9000)"
> > Title = "Choose an Employee"
> > Default = "7654"
> >
> > On Error GoTo err_test
> >
> > EmpNoValue = InputBox(Message, Title, Default)
> > If EmpNoValue = "" Then Exit Sub
> > If EmpNoValue < 5000 Or EmpNoValue > 9000 Then EmpNoValue = 7654
> >
> > Set Oracon = CreateObject("ADODB.Connection")
> > Oracon.ConnectionString = "Provider=OraOLEDB.Oracle;" & _
> > "Data Source=exampledb;" & _
> > "User ID=scott;" & _
> > "Password=tiger;"
> >
> > Oracon.Open
> > Set cmd.ActiveConnection = Oracon
> > Set param1 = cmd.CreateParameter("param1", adSmallInt, adParamInput, ,
> > EmpNoValue)
> > cmd.Parameters.Append param1
> > Set param2 = cmd.CreateParameter("param2", adSmallInt, adParamOutput)
> > cmd.Parameters.Append param2
> >
> > ' Enable PLSQLRSet property
> > Cmd.Properties ("PLSQLRSet") = TRUE
> >
> > cmd.CommandText = "{CALL Employees.GetDept(?, ?)}"
> > Set recset = cmd.Execute
> >
> > ' Disable PLSQLRSet property
> > Cmd.Properties ("PLSQLRSet") = FALSE
> >
> > MsgBox "Number: " & EmpNoValue & " Dept: " &
recset.Fields("deptno").Value
> >
> > Exit Sub
> >
> > err_test:
> > MsgBox Error$
> > For Each objErr In Oracon.Errors
> > MsgBox objErr.Description
> > Next
> > Oracon.Errors.Clear
> > Resume Next
> >
> > ----End code sample.
> >
> > Is this incorrect?
>
> Properly handled errors in the database never produce errors in a
front-end.
> That you are handling errors as you are indicates the database is not
handling
> them: Nothing more.
>
> Daniel Morgan
>

You cannot be more wrong. I don't care if it's java, c++, vb6, ms.net, or some other language, if you throw an exception in the database, an exception is going to be thrown in the front end app. If you do not handle exceptions in the front end app, that app is going to terminate. (The front end would have to let the user know that there was a failure)

By the way, this is not my code, it is Oracle's.

Here is the same syntax (on error goto in vb6) in java (taken from developer.java.sun.com)

   try
    {

       // some DB work
    } // end try
    catch ( SQLException SQLe) //
    {

      while( SQLe != null)
      {
        // do handling

        SQLe = SQLe.getNextException();
      }

    } // end catch Received on Sun Apr 20 2003 - 21:00:45 CDT