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Q305995: PRB: Error When You Connect to a Jet Database on a Novell Server

Article: Q305995
Product(s): Microsoft C Compiler
Version(s): 3.51,3.6
Operating System(s): 
Keyword(s): kberrmsg kbJET kbGrpDSVBDB kbDSupport
Last Modified: 11-JUN-2002

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The information in this article applies to:

- The DAO SDK, versions 3.51, 3.6 
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IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

  Q256986 Description of the Microsoft Windows Registry

SYMPTOMS
========

When you try to use Data Access Objects (DAO) to connect to a Microsoft Jet
database on a Novell fileserver, you may receive the following error message:

  3050 Could not lock file.

CAUSE
=====

This problem occurs because Novell fileservers have a maximum number of locks
setting, and Jet may use a high number locks when it reads or writes an .mdb
file.

RESOLUTION
==========

There are several ways to work around this behavior:

- Use Regedit.exe or Regedt32.exe to edit the Windows Registry, and permanently
  change the MaxLocksPerFile value.

- Use the SetOption method of the DBEngine object to temporarily change the
  MaxLocksPerFile value in the code.

Method 1: Change MaxLocksPerFile in the Windows Registry:

WARNING: If you use Registry Editor incorrectly, you may cause serious problems
that may require you to reinstall your operating system. Microsoft cannot
guarantee that you can solve problems that result from using Registry Editor
incorrectly. Use Registry Editor at your own risk.

1. From the Windows Start menu, click Run, type "Regedt32.exe" (without the
  quotation marks), and then click OK to start Registry Editor.

2. Locate the MaxLocksPerFile value under the following key in the registry:

  HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Jet\4.0\Engines\Jet 4.0

  NOTE: If the MaxLocksPerFile value does not exist, you must create it.

3. Decrease the MaxLocksPerFile value.

4. Quit Registry Editor.

NOTE: This method changes the Windows Registry setting for all applications that
use the Microsoft Jet database engine version 4.0.

Method 2: Use SetOption to Change MaxLocksPerFile Temporarily:

Microsoft provides programming examples for illustration only, without warranty
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warranties of merchantability and/or fitness for a particular purpose. This
article assumes that you are familiar with the programming language being
demonstrated and the tools used to create and debug procedures. Microsoft
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  http://www.microsoft.com/partner/referral/

For more information about the support options that are available and about how
to contact Microsoft, visit the following Microsoft Web site:

  http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

The SetOption method temporarily overrides values for the Microsoft Jet database
engine keys in the Windows Registry. The new value remains in effect until you
change it again or until the DBEngine object is closed.

The following code sample sets MaxLocksPerFile to 128 before it runs an update
operation inside a transaction:

  Sub MDBUpdate()
     On Error GoTo MDBUpdate_Error
     Dim db As DAO.Database, ws As DAO.Workspace

     ' Set MaxLocksPerFile.
     DBEngine.SetOption dbMaxLocksPerFile, 128

     Set db = CurrentDb
     Set ws = Workspaces(0)

     ' Perform the update.
     ws.BeginTrans
     db.Execute "UPDATE TableName SET Field1 = 'Updated Field'", _
           dbFailOnError

     ws.CommitTrans

     db.Close
     MsgBox "Done!"
     Exit Sub

  MDBUpdate_Error:
     MsgBox Err & " " & Error
     ws.Rollback
     MsgBox "Operation Failed - Update Canceled"
  End Sub

STATUS
======

This behavior is by design.

Additional query words:

======================================================================
Keywords          : kberrmsg kbJET kbGrpDSVBDB kbDSupport 
Technology        : kbAudDeveloper kbDAOsearch kbSDKDAOSearch kbSDKSearch kbSDKDAO360 kbSDKDAO351
Version           : :3.51,3.6
Issue type        : kbprb

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