HOWTO: Use a Custom Jet Profile to Alter Data Access Behavior (173646)

MORE INFORMATION

In 16-bit versions of Visual Basic and Microsoft Access, Jet settings are stored in an .ini file (for example, Msaccess.ini or Msacc20.ini). You can provide a custom .ini file with your application that contains settings specific to your application.

The 32-bit versions of Jet read their settings from the registry.

In Visual Basic 4.0, 5.0, 6.0, and Jet versions 3.0 and 3.5 use the default registry location:

-or-

If using Microsoft Access, settings are read from the following branch first, and then the default location (above) is used for any additional values:

-or-

To prevent multiple applications from making custom changes to these settings and negatively impacting other Jet-based programs, the application can tell Jet to read its settings from a different branch of the registry. These alternate branches are known as Profiles.

You don't have to reproduce the entire registry branch in your profile. Values you specify in your custom profile override values specified in the default registry location, which in turn override internal Jet default values.

Example Profile

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT, you should also update your Emergency Repair Disk (ERD).

This example illustrates registry changes for a custom profile that lowers the LockRetry setting from the default value of 20 to 5.

1. In the Registry Editor, expand HKEY_LOCAL_MACHINE\SOFTWARE and add key values for your company name (MyCorp), application name (MyApp), and version (1.0):
   
   HKEY_LOCAL_MACHINE\SOFTWARE\MyCorp\MyApp\1.0
2. The above is sufficient for Visual Basic, but to maintain compatibility with Microsoft Access applications, add keys for "Jet" and "3.0" or "3.5":
   
   HKEY_LOCAL_MACHINE\SOFTWARE\MyCorp\MyApp\1.0\Jet\3.0
   
   -or-
   
   HKEY_LOCAL_MACHINE\SOFTWARE\MyCorp\MyApp\1.0\Jet\3.5
3. This is an empty Profile. From here, add keys and values that affect Jet's behavior. To make the LockRetry changes, add the keys "Engines" and "Jet":
   
   HKEY_LOCAL_MACHINE\SOFTWARE\MyCorp\MyApp\1.0\Jet\3.0\Engines\Jet
   
   -or-
   
   HKEY_LOCAL_MACHINE\SOFTWARE\MyCorp\MyApp\1.0\Jet\3.5\Engines\Jet
   
   Then, add a REG_DWORD Value, called LockRetry, and a value of 5.
   The profile is complete.
   

   Using the Profile in Visual Basic

   To use the profile in Visual Basic, set DBEngine.IniPath to the profile name prior to using any database functionality:
   
   In Visual Basic 4.0:
   

      DBEngine.IniPath = _
        "HKEY_LOCAL_MACHINE\SOFTWARE\MyCorp\MyApp\1.0\Jet\3.0"

   
   In Visual Basic 5.0:
   

      DBEngine.IniPath = _
        "HKEY_LOCAL_MACHINE\SOFTWARE\MyCorp\MyApp\1.0\Jet\3.5"

   
   

   Using the Profile in Microsoft Access

   Unlike visual Basic, where you can set the profile name programmatically, Jet is already initialized by the time your Microsoft Access code is running. To specify a profile name, you need to add another registry key to specify a "friendly" profile name and use a command-line switch when starting Microsoft Access:
   
   1. Expand the following registry branch:
      
      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Access\7.0
      
      -or-
      
      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\8.0\Access
   2. Add a key "Profiles".
      
      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Access\7.0\Profiles
      
      -or-
      
      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\8.0\Access\Profiles
   3. Add a REG_SZ value with the name being your "friendly" profile name (for example, MyProfile) and the value being the registry branch where the profile settings are located. For example:

            Name:  MyProfile
            Type:  REG_SZ
            Value: HKEY_LOCAL_MACHINE\SOFTWARE\MyCorp\MyApp\1.0
      

   4. Start Microsoft Access with the command-line option:
      
      MSACCESS.EXE /PROFILE "MyProfile" MYDATABASE.MDB
   Microsoft Access 95 will automatically choose the ...\Jet\3.0 branch, Microsoft Access 97 will automatically choose the ...\Jet\3.5 branch, in Visual Basic you must specify the complete profile path.
   
4. Because you can't guarantee that Microsoft Access was started using the correct profile, you can check your startup code to see if the user started the application properly or just double-clicked the icon for the

.mdb file. For example:

      If SysCmd(acSysCmdProfile) <> "MyProfile" Then
        MsgBox "To use this database, run MyApp from the Start Menu"
        DoCmd.Quit acExit
      End If

Compatibility with Earlier Jet Databases

If the database you're opening is used by earlier versions of Jet (1.0, 1.1, 2.0, or 2.5), Microsoft Jet 3.x doesn't read these files directly. It uses an Installable ISAM engine in the same way it would when reading a dBase or Paradox file.

For example, to set the LockRetry value for accessing a Jet 2.x database, add the Value to the following location:

You still only reference the profile location as indicated in the Microsoft Access and Visual Basic usage sections above. For example:

In Visual Basic:

   DBEngine.IniPath = _
     "HKEY_LOCAL_MACHINE\SOFTWARE\MyCorp\MyApp\1.0\Jet\3.0"

   DBEngine.IniPath = _
     "HKEY_LOCAL_MACHINE\SOFTWARE\MyCorp\MyApp\1.0\Jet\3.5"

In Microsoft Access:

Table of Engine Keys

The following table lists registry branches for the Jet 3.x engine and the various other engines:

   Engine     Registry Branch
   ----------------------------------------------------
   Jet 3.x    ...\Engines\Jet
   Jet 2.x    ...\Engines\Jet 2.x\ISAM
   ODBC       ...\Engines\ODBC
   Xbase      ...\Engines\Xbase
   Paradox    ...\Engines\Paradox
   Excel      ...\Engines\Excel
   Lotus      ...\Engines\Lotus
   Text       ...\Engines\Text

Jet 3.5 Notes

With Jet 3.5, you can tune some values dynamically using the new SetOption method of the DBEngine object. This means you can use some values for one part of your program, that is, to favor a bulk update, while using other values in another part of your program, that is, to favor interactive data entry. Using DBEngine.SetOption affects only the current instance of your program. It can be used in Microsoft Access 97 and Visual Basic 5.0.

The following table lists the settings you can change:

   Setting                 Constant
   ---------------------------------------------------
   PageTimeout             dbPageTimeout
   SharedAsyncDelay        dbSharedAsyncDelay
   ExclusiveAsyncDelay     dbExclusiveAsyncDelay
   LockRetry               dbLockRetry
   UserCommitSync          dbUserCommitSync
   ImplicitCommitSync      dbImplicitCommitSync
   MaxBufferSize           dbMaxBufferSize
   MaxLocksPerFile         dbMaxLocksPerFile
   LockDelay               dbLockDelay
   RecycleLVs              dbRecycleLVs
   FlushTransactionTimeout dbFlushTransactionTimeout

Usage:

   DBEngine.SetOption dbMaxBufferSize, 128