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Thread: [RESOLVED] Process cannot access a file because it is being used by another process

  1. #1

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    Resolved [RESOLVED] Process cannot access a file because it is being used by another process

    Hi,



    I frequently encounter “Process cannot access a file because it is being used by another process” error when trying to perform a file function (eg delete) that requires the Access Database file to be closed.

    I open the database file in exclusive user mode as follows:
    Dim ltStr As String

    ltStr = "Provider=Microsoft.Jet.OLEDB.4.0; "

    ltStr &= " Data Source=" + gtPath + "\abc.mdb; "

    ltStr &= " Mode = Share Deny Read |Share Deny Write; "

    ltStr &= " Jet OLEDBatabase Password= '" & gtPassWord & "'"

    oCon = New OleDbConnection(ltStr)

    oCon.Open()



    I attempt to delete the file with the following code :

    oCon.Close()

    oCon.Dispose()

    System.IO.File.Delete("abc.mdb")

    This works only about 5% of the time – 95% crashing with the process error described above.



    I can dramatically improve the success rate to about 70% using the following code to try and close / dispose the connection multiple times

    Do

    TryAgain:

    Try

    System.IO.File.Delete("abc.mdb")

    Catch ex As Exception

    oCon.Close()

    oCon.Dispose()

    liCount = liCount + 1

    If liCount > 10 Then

    li = MsgBox("Can not Delete Files as they are still being used" & Chr(10) & "Do you wish to try again", MsgBoxStyle.YesNo, "Deletion Failed")

    If li = 6 Then

    GoTo TryAgain

    Else

    Exit Sub

    End If

    End Try

    Application.DoEvents()

    Loop



    Is there anyway I can force the immediate closure of the connection so as to ensure the deletion works 100% of the time?

    I am only opening the connection once at the start of the program.
    Is this wrong – should I be opening / closing the connection at the start and end of each database query and update

  2. #2
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    Re: Process cannot access a file because it is being used by another process

    Is this a single user application ?
    Are you viewing the mdb file using Access when you run the app ?
    JG


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  3. #3
    PowerPoster kevininstructor's Avatar
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    Re: Process cannot access a file because it is being used by another process

    It seems strange that if you close the database as soon as you are done with it then sometime goes by you attempt to remove it and fails says to me the database connection is still open or (not knowing your environment) another process has the database open

    While the MDB is open there will be a lock file present, until it goes away you cannot remove the MDB.

    Before you attempt to remove the MDB try the following. When trying the following out make sure you do not have MS-Access application open.


    Code:
    Msgbox("Waiting")
    System.IO.File.Delete("abc.mdb")
    When the message box appears traverse to the folder with abc.mdb and see if abc lock file exists which is the lock file. If the lock file exists then the delete will fail while if the lock file is not there you can delete the file.

    One possible solution would be to go into a loop to remove the file. The intent is to allow time for the file to close. When trying the following out make sure you do not have MS-Access application open.

    Example
    Code:
    ''' <summary>
    ''' Remove MS-Access database
    ''' </summary>
    ''' <param name="FileName">Database to remove</param>
    ''' <param name="WaitTime">Sleep time</param>
    ''' <param name="Loops">How many attempts to try</param>
    ''' <remarks></remarks>
    Function RemoveAccessDatabase( _
        ByVal FileName As String, _
        ByVal WaitTime As Integer, _
        ByVal Loops As Integer) As Boolean
    
        Dim Success As Boolean = False
    
        Dim LockFile As String = IO.Path.ChangeExtension(FileName, "ldb")
    
        For Counter As Integer = 0 To Loops
            If IO.File.Exists(LockFile) Then
                System.Threading.Thread.Sleep(WaitTime)
                IO.File.Delete(FileName)
            Else
                Success = True
                Exit For
            End If
        Next
    
        Return Success
    
    End Function
    Now call it as follows
    Code:
    oCon.Close()
    RemoveAccessDatabase("abc.mdb", 100, 5)
    Let's say that fails, increase the second param in 100 increments until it does work.

    On a different topic you need to avoid Go To statements as they can cause more problems then they are worth. Learn how to code without them.
    Last edited by kevininstructor; Aug 20th, 2011 at 03:07 PM. Reason: Wording

  4. #4

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    Re: Process cannot access a file because it is being used by another process

    Quote Originally Posted by jggtz View Post
    Is this a single user application ?
    Are you viewing the mdb file using Access when you run the app ?
    Yes this is a single user application.

    The application reads and writes to the MDB file but these operations are completed well before trying to delete the file.

    There appears for some unknown reason a delay in closing the connection.

  5. #5

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    Re: Process cannot access a file because it is being used by another process

    Quote Originally Posted by kevininstructor View Post
    It seems strange that if you close the database as soon as you are done with it then sometime goes by you attempt to remove it and fails says to me the database connection is still open or (not knowing your environment) another process has the database open

    While the MDB is open there will be a lock file present, until it goes away you cannot remove the MDB.

    Before you attempt to remove the MDB try the following. When trying the following out make sure you do not have MS-Access application open.


    Code:
    Msgbox("Waiting")
    System.IO.File.Delete("abc.mdb")
    When the message box appears traverse to the folder with abc.mdb and see if abc lock file exists which is the lock file. If the lock file exists then the delete will fail while if the lock file is not there you can delete the file.

    One possible solution would be to go into a loop to remove the file. The intent is to allow time for the file to close. When trying the following out make sure you do not have MS-Access application open.

    Example
    Code:
    ''' <summary>
    ''' Remove MS-Access database
    ''' </summary>
    ''' <param name="FileName">Database to remove</param>
    ''' <param name="WaitTime">Sleep time</param>
    ''' <param name="Loops">How many attempts to try</param>
    ''' <remarks></remarks>
    Function RemoveAccessDatabase( _
        ByVal FileName As String, _
        ByVal WaitTime As Integer, _
        ByVal Loops As Integer) As Boolean
    
        Dim Success As Boolean = False
    
        Dim LockFile As String = IO.Path.ChangeExtension(FileName, "ldb")
    
        For Counter As Integer = 0 To Loops
            If IO.File.Exists(LockFile) Then
                System.Threading.Thread.Sleep(WaitTime)
                IO.File.Delete(FileName)
            Else
                Success = True
                Exit For
            End If
        Next
    
        Return Success
    
    End Function
    Now call it as follows
    Code:
    oCon.Close()
    RemoveAccessDatabase("abc.mdb", 100, 5)
    Let's say that fails, increase the second param in 100 increments until it does work.

    On a different topic you need to avoid Go To statements as they can cause more problems then they are worth. Learn how to code without them.
    Hi,

    Thanks for the suggestion. I will certainly give it a try.
    The problem however is that the required waittime varies each time I run the application in the development time. I will need to use a very pessimistic time in a run time enviroment.

    What I was really hoping for is an instruction to kill the connection whether it is open and/or in use.

  6. #6
    PowerPoster kevininstructor's Avatar
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    Re: Process cannot access a file because it is being used by another process

    Quote Originally Posted by Jeff Las View Post
    Hi,

    Thanks for the suggestion. I will certainly give it a try.
    The problem however is that the required waittime varies each time I run the application in the development time. I will need to use a very pessimistic time in a run time enviroment.

    What I was really hoping for is an instruction to kill the connection whether it is open and/or in use.
    First off there is no "unknown reason" for the connection to stay open. I would suggest the following if you tried my other suggestion.

    Get rid of the current connection object and replace with the following

    Code:
    Dim cb As New OleDbConnectionStringBuilder
    
    cb.Provider = "Microsoft.Jet.OLEDB.4.0"
    cb.DataSource = IO.Path.Combine(gtPath, "abc.mdb")
    cb("Mode") = "Share Deny Read |Share Deny Write"
    cb("Jet OLEDBatabase Password") = gtPassWord
    
    
    Using oCon As New OleDbConnection(cb.ConnectionString)
        '
        ' Do what you came to do
        '
    End Using
    After the Using statement code has completed the connection is then closed. If for some reason the database is still open it is because of something else has it open.

  7. #7
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    Re: Process cannot access a file because it is being used by another process

    i'd try adding a
    vb Code:
    1. Threading.Thread.Sleep(1000)
    before the file delete.

  8. #8
    PowerPoster kevininstructor's Avatar
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    Re: Process cannot access a file because it is being used by another process

    Quote Originally Posted by TCarter View Post
    i'd try adding a
    vb Code:
    1. Threading.Thread.Sleep(1000)
    before the file delete.
    What happened?

  9. #9
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    Re: Process cannot access a file because it is being used by another process

    I use the following code, which is generally successful:
    Code:
        Function SafeFileDelete(ByVal FileName As String) As Boolean
            If My.Computer.FileSystem.FileExists(FileName) Then
                For i As Integer = 1 To 10
                    Try
                        My.Computer.FileSystem.DeleteFile(FileName)
                        Exit For
                    Catch ex As Exception
                        If i = 10 Then
                            AddToLog("Unable to delete file " & FileName & " after 10 tries over 10 seconds. Exception says " & ex.Message)
                        Else
                            MySleep(1)    ' same as Threading.Thread.Sleep(1000)
                        End If
                    End Try
                Next
            End If
    
            Return My.Computer.FileSystem.FileExists(FileName)
        End Function
    I have this function running as part of a project that goes all day long, and maybe once an hour this code fails & I see in the log that the file was not in fact deleted, always due to the "Process cannot access a file because it is being used by another process" exception.

    What I'm puzzled by, is WHAT other process is doing this? I'd really like to capture this info in the log, since the larger program needs to run continuously (it tolerates the failed-to-delete fault), rather than stopping to wait while I troubleshoot (hoping that the "other process" doesn't let go before I get to the keyboard). Can anybody point me to some code that will allow the program to determine what the "other process" is?

    Thanks!

  10. #10
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    Re: Process cannot access a file because it is being used by another process

    Quote Originally Posted by kevininstructor View Post
    What happened?
    eh? not my thread.. was offering a suggestion.

  11. #11

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    Re: Process cannot access a file because it is being used by another process

    Hi,

    Thanks to all who have replied.
    I am using KevinInstructors Removeaccessdatabase function as a quick fix - it is 90&#37; successful.

    I will be trying his alternative solution when I have some free time.

    Thanks

  12. #12
    PowerPoster kevininstructor's Avatar
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    Re: [RESOLVED] Process cannot access a file because it is being used by another proce

    Since you still have problems I would recommend downloading Process Monitor which by default monitors all applications running but you can have PM monitor just your application which should point you to the problem. Take time to learn how to filter what to monitor besides just your application such as filter out registry monitoring, if you do not you will have a lot to wad thru.

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