When you perform an operation on a table, you may receive the following error message if the operation creates a large number of page locks: If you run an action query on a large table, you may receive the following error message:

The page locks required for the transaction exceed the MaxLocksPerFile value, which defaults to 9500 locks. The MaxLocksPerFile setting is stored 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: There are several ways to work around this problem:

• You can use Regedit.exe to edit the registry and change the MaxLocksPerFile value permanently.
• You can use the SetOption method of the DBEngine object to change the MaxLocksPerFile value temporarily in code.
• If the error occurs when you run an action query, you can modify the query and set its UseTransaction property to No.

Method 1: Changing MaxLocksPerFile in the registry

Use Registry Editor to increase the MaxLocksPerFile value under the following key: Note that this method changes the registry setting for all applications that use Microsoft Jet database engine version 4.0.

Method 2: Using SetOption to change MaxLocksPerFile Temporarily

NOTE: The sample code in this article uses Microsoft Data Access Objects. For this code to run properly, you must reference the Microsoft DAO 3.6 Object Library. To do so, click References on the Tools menu in the Visual Basic Editor, and make sure that the Microsoft DAO 3.6 Object Library check box is selected.

Microsoft provides programming examples for illustration only, without warranty either expressed or implied. This includes, but is not limited to, the implied warranties of merchantability or fitness for a particular purpose. This article assumes that you are familiar with the programming language that is being demonstrated and with the tools that are used to create and to debug procedures. Microsoft support engineers 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 requirements. The SetOption method temporarily overrides values for the Microsoft Jet database engine keys in the registry. The new value remains in effect until you change it again, or until the DBEngine object is closed.

Note Changes made to the MaxLocksPerFile setting by using the SetOption method will only be available through the current session of Data Access Objects (DAO). Queries that are run through the Microsoft Access user interface will still use the settings in the registry.

The following code sample sets MaxLocksPerFile to 200,000 before executing an update operation inside a transaction:

Method 3: Setting the UseTransaction property in an action query

If a stored action query causes the error, you can set its UseTransaction property to No. Note that if you do this, you cannot roll back your changes if there is a problem or an error while the query is running:

1. Open the query in Design view.
2. On the View menu, click Properties.
3. Click an empty space in the upper half of the query window to display the Query Properties dialog box.
4. Set the UseTransaction property to No.
5. Save the query and close it.

The MaxLocksPerFile setting in the registry prevents transactions in the Microsoft Jet database engine from exceeding a specified value. If a transaction tries to create locks in excess of the MaxLocksPerFile value, the transaction is split into two or more parts and partially committed.

Steps to reproduce the problem

The following example uses a Visual Basic procedure to create a table with 10,000 records in it, and then modifies the table in order to cause the error message:

1. Open the sample database Northwind.mdb.
2. Create a module, and then type the following procedure:

   Sub CreateBigTable()
      Dim db As Database, rs As Recordset
      Dim iCounter As Integer, strChar As String
      Set db = CurrentDb
      db.Execute "CREATE TABLE BigTable (ID LONG, Field1 TEXT(255), " & _
        "Field2 TEXT(255), Field3 TEXT(255), Field4 TEXT(255))", _
        dbFailOnError
      Set rs = db.OpenRecordset("BigTable", dbOpenDynaset)
      iCounter = 0
      strChar = String(255, " ")
      While iCounter <= 10000
         rs.AddNew
         rs!ID = iCounter
         rs!Field1 = strChar
         rs!Field2 = strChar
         rs!Field3 = strChar
         rs!Field4 = strChar
         rs.Update
         iCounter = iCounter + 1
      Wend
      MsgBox "Done!"
   End Sub
   					

3. To run the procedure, type the following line in the Immediate window, and then press ENTER:

   CreateBigTable
   						

   
   The procedure creates a table called BigTable with 10,000 records in it.
4. Save the module as Module1, and then close it.
5. Open the BigTable table in Design view.
6. Change the FieldSize property of Field4 to 253.
7. Save the table. Click Yes when you are prompted that some data may be lost. Note that, after a while, you receive the following error messages:
   Microsoft Access can't change the data type.
   There isn't enough disk space or memory.
   Errors were encountered during the save operation. Data types were not changed. Properties were not updated.