Why is my Access database not up-to-date when I read it from another process?

Question

In my application I do the follwing things:

1. Open a Access database (.mdb) using Jet/ADO and VB6
2. Clear and re-fill a table with new data
3. Clos

Answer 1

This Microsoft Knowledge Base article explains how to do it.

Here's an excerpt with sample code. The code uses two connections from one process, so you need to pull the reading part into your second process.

1. The writer must start a transaction, using ADO's Connection.BeginTrans, prior to writing the data.
2. The writer must make the database updates and then commit the transaction (using ADO's Connection.CommitTrans).
3. The reader must call JRO.JetEngine.RefreshCache passing in it's connection prior to attempting to read the data.

Note that JRO.JetEngine is included by adding a reference to the Microsoft Jet And Replication Objects 2.1 Library to your VB project.

    Sub SyncReadDemo()
    Dim conn1 As New ADODB.Connection
    Dim conn2 As New ADODB.Connection
    Dim rs As New ADODB.recordset
    Dim JRO As New JRO.JetEngine
    Dim strConnect As String
    Dim i As Long


  ' Set up our connection string (requires a database named c:\db1.mdb).
    strConnect = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=c:\db1.mdb"

    ' Open connection 1 and drop and re-create test table.
    conn1.CursorLocation = adUseServer
    conn1.Open strConnect
    On Error Resume Next
    conn1.Execute "drop table tmpTest", , _
        adExecuteNoRecords + adCmdText
    On Error GoTo 0
    conn1.Execute "create table tmpTest (id long)", , _
        adExecuteNoRecords + adCmdText

    ' Close connection 1 to flush the creation of table tmpTest. 
    conn1.Close

    ' Now open connection 1 and connection 2.
    conn1.Open strConnect
    conn2.Open strConnect

    ' Insert 10 records using connection 1.
    ' Note we must perform all writes inside of a transaction.
    conn1.BeginTrans
    For i = 1 To 10
        conn1.Execute "insert into tmpTest (id) values (1)", , _
            adExecuteNoRecords + adCmdText
    Next i
    conn1.CommitTrans

    ' Refresh cache for reader connection.
    JRO.RefreshCache conn2
    Set rs = conn2.Execute("select * from tmpTest", , adCmdText)

    ' Count records in our table (should be 10).
    i = 0
    While Not rs.EOF
        i = i + 1
        rs.MoveNext
    Wend
    rs.Close

    MsgBox "Read " & i & " records using different connections."

    conn1.Close
    conn2.Close

End Sub