PRB: Error "3050 Could Not Lock File" When You Connect to a Jet Database on a Novell Server

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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.


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.


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

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows
  1. From the Windows Start menu, click Run, type Regedt32.exe, 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

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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.
db.Execute "UPDATE TableName SET Field1 = 'Updated Field'", _


MsgBox "Done!"
Exit Sub

MsgBox Err & " " & Error
MsgBox "Operation Failed - Update Canceled"
End Sub


This behavior is by design.

Artikelnummer: 305995 – Letzte Überarbeitung: 19.06.2014 – Revision: 1