ACC97: How to Read .LDB Files

• 
  Microsoft Access 97


• 
  Microsoft Visual Basic for Applications

SUMMARY

Advanced: Requires expert coding, interoperability, and multiuser skills.





In Microsoft Access 97, the .ldb file is used to determine which records
are locked in a shared database and by whom. It is created automatically
when any user opens a database and deleted when the last user closes the
database. While the .ldb file cannot be opened directly for reading,
Microsoft provides a dynamic link library that exposes functions that you
can use to read the .ldb file. This article contains sample code for using
the DLL to read an .ldb file.




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that you are familiar with the programming language being demonstrated and the
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MORE INFORMATION

The dynamic link library Msldbusr.dll contains functions that enable you to
do the following:

• View all computers that have logged into a database since the .ldb file
  was created.
  



• View only computers that are currently logged into a database.
  



• View computers that are causing a database file to be corrupted.
  



• View the count of computers logged into a database.
  

Q176670
ACC: Microsoft Jet Utilities Available in Download Center

1. Create a new module in Microsoft Access 97
   



2. Type or paste the following function declaration statement into the
   Declarations section of the module:




  
      Declare Function LDBUser_GetUsers Lib "MSLDBUSR.DLL" _  
      (lpszUserBuffer() As String, ByVal lpszFilename As String, _  
      ByVal nOptions As Long) As Integer 

3. Type or paste the following sample function into the module:




  
      Public Function GetUsers(Optional StrDbPath As String)  
  
         ReDim lpszUserBuffer(1) As String  
         Dim intLooper As Integer  
         Dim Cusers As Long  
         Dim strMsgBox As String  
  
         On Error GoTo Err_GetUsers  
  
         ' Check to see if a database path was passed  
         ' to the function. If the argument was not used,  
         ' assume that we're to investigate the .ldb  
         ' of the current database.  
         If IsMissing(StrDbPath) Or StrDbPath = "" Then  
              StrDbPath = CurrentDb.Name  
         End If  
  
         ' Set Cusers to the number of computers currently connected  
         ' to the database. Insert computer information into the  
         ' lpszUserBuffer array.  
  
         ' Arguments of LdbUser_Get Users:  
         ' 1 =   All users who have logged in since the LDB file was  
         ' created  
         ' 2 =   Only users who are currently logged in  
         ' 4 =   Only users who are causing the database file to be  
         ' corrupted  
         ' 8 =   Just return the count of users  
  
         Cusers = LDBUser_GetUsers(lpszUserBuffer(), StrDbPath, 2)  
  
         ' Print possible errors returned by the function.  
         Select Case Cusers  
              Case -1  
                   strMsgBox = "Can't open the LDB file"  
              Case -2  
                   strMsgBox = "No user connected"  
              Case -3  
                   strMsgBox = "Can't Create an Array"  
              Case -4  
                   strMsgBox = "Can't redimension array"  
              Case -5  
                   strMsgBox = "Invalid argument passed"  
              Case -6  
                   strMsgBox = "Memory allocation error"  
              Case -7  
                   strMsgBox = "Bad index"  
              Case -8  
                   strMsgBox = "Out of memory"  
              Case -9  
                   strMsgBox = "Invalid Argument"  
              Case -10  
                   strMsgBox = "LDB is suspected as corrupted"  
              Case -11  
                   strMsgBox = "Invalid argument"  
              Case -12  
                   strMsgBox = "Unable to read MDB file"  
              Case -13  
                   strMsgBox = "Can't open the MDB file"  
              Case -14  
                   strMsgBox = "Can't find the LDB file"  
         End Select  
  
         If Not IsEmpty(strMsgBox) And strMsgBox <> "" Then  
              MsgBox strMsgBox, vbCritical, "Error"  
              Exit Function  
         End If  
  
         ' Print computer names to Debug window.  
         For intLooper = 0 To Cusers - 1  
              Debug.Print "User"; intLooper + 1; ":"; _  
              lpszUserBuffer(intLooper)  
         Next  
  
    Exit_GetUsers:  
         Exit Function  
    Err_GetUsers:  
         MsgBox Err.Description  
         Resume Exit_GetUsers  
  
    End Function 

4. To test this function, type the following line in the Debug window, and then press ENTER:




  
?getusers() 

REFERENCES

For more information about Msldbusr.dll, review the Msldbusr.doc file found
in Jetutils.exe.

Additional query words:
inf locking