PATCH: Out of Memory Error w/ AddNew/Update on Dynaset/Table

The information in this article applies to:

• Professional Edition of Microsoft Visual Basic for Windows, version 3.0

SYMPTOMS

Performing an AddNew and then and Update method on a table or dynaset causes the Jet database engine to allocate a small amount of memory that is not released until the Jet database engine is unloaded from memory. Therefore, programs that perform many Updates over a long period of time without unloading the Jet database engine will eventually result in an "Out of Memory" error.

RESOLUTION

There are two possible workarounds:

Update Vbdb300.dll to version 3.00.0530, dated 1 Feb 95 by downloading Vbdb300.exe. You can find Vbdb300.exe, a self-extracting file, on these services:

The following file is available for download from the Microsoft Software Library:

 ~ vbdb300.exe (size: 63762 bytes) 

   ARTICLE-ID: Q119591
   TITLE     : How to Obtain Microsoft Support Files from
               Online Services

   NOTE: This version of the Vbdb300.dll does require the VB/Access
   compatibility layer (Comlyr.exe) and the updated Jet engine in the
   Access Service Pack (Accsvc.exe in the GO MSACCESS forum).

   DISCLAIMER: The version of Vbdb300.dll (hereinafter the “Product”) is
   being released as a patch (the “Patch”) in order to fix a specific
   problem a few customers are experiencing with Microsoft Visual Basic
   3.0. This Patch has been tested comprehensively to ensure that no errors
   or additional problems are introduced into the Product during normal
   usage. However, in order to release this Patch as quickly as possible,
   it has not have been subjected to the same series of rigorous functional
   and regression tests that are used for regular production products.
   Consequently, this Patch should be installed only if you are
   experiencing the specific problem mentioned above, and not applied
   indiscriminately. Use of this Patch is governed by all of the provisions
   of the Microsoft End User Software License Agreement included with the
   Product, as if it were the Product.

   In addition, the Patch is provided to you at no additional charge.
   Microsoft Corporation owns all right, title and interest in and to the
   Patch.

   Copyright 1995 Microsoft Corporation, All Rights Reserved.

Periodically shell to another Visual Basic program that does not use the Jet database engine to unload the database application. This will cause all of the memory held by the Jet database engine to be released back to the system. You can then restart your application from the non-database program.

STATUS

This bug in Microsoft Visual Basic for Windows version 3.0 was corrected with Vbdb300.dll version 3.00.0530 dated 1 Feb 95.

MORE INFORMATION

This problem is not corrected by using the Microsoft Access 2.0/Visual Basic 3.0 Compatibility Layer; nor is it corrected by using the Microsoft Access version 2.0 Service Pack.

Steps to Reproduce Behavior

NOTE: You will need the older version 3.00.0529 of Vbdb300.dll and the Professional Edition of Visual Basic to reproduce the problem outlined below.

1. Create a new project. Form1 is created by default.

2. Add a label control to Form1.

3. Enter the following code for Form1:

      'Enter the following lines as one line
      Declare Function GetFreeSpace Lib "kernel" (ByVal flag As Integer) _
         As Long
   
      Sub Form_Activate ()
         Dim lngStartMem As Long
         Dim lngUsedMem As Long
         Dim lngRec As Long
         Dim strMsg as String
         Dim dbBiblio As Database
         Dim dsAuthors As Dynaset
   
         Label1.Caption = "Initializing..."
         Label1.Refresh
   
         Set dbBiblio = OpenDatabase("biblio.mdb")
         Set dsAuthors = dbBiblio.CreateDynaset("Authors")
         lngStartMem = GetFreeSpace(0)
   
         BeginTrans
         For lngRec = 1 To 100000
            dsAuthors.AddNew
            dsAuthors("Au_ID") = lngRec + 100
            dsAuthors("Author") = "Doe, John"
            dsAuthors.Update
            If lngRec Mod 500  = 0 Then
               CommitTrans
               lngUsedMem = lngStartMem - GetFreeSpace(0)
               strMsg = "Records: " & CStr(lngRec) & Chr$(13) & Chr$(10)
               strMsg = strMsg & "Used: " & CStr(lngUsedMem)
               Label1.Caption = strMsg
               Label1.Refresh
               BeginTrans
            End If
         Next
         CommitTrans
   
         dsAuthors.Close
         dbBiblio.Close
      End Sub
   
   

4. Run the program. The "Used:" line of the label tells how much memory has been allocated from the global memory heap. This memory is not recovered until you exit from Visual Basic.