DOCUMENT:Q305995  11-JUN-2002  [visualc]
TITLE   :PRB: Error When You Connect to a Jet Database on a Novell Server
PRODUCT :Microsoft C Compiler
PROD/VER::3.51,3.6
OPER/SYS:
KEYWORDS:kberrmsg kbJET kbGrpDSVBDB kbDSupport

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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
either expressed or implied, including, but not limited to, the implied
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
support professionals can help explain the functionality of a particular
procedure, but they will not modify these examples to provide added
functionality or construct procedures to meet your specific needs. If you have
limited programming experience, you may want to contact a Microsoft Certified
Partner or the Microsoft fee-based consulting line at (800) 936-5200. For more
information about Microsoft Certified Partners, please visit the following
Microsoft Web site:

   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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