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Opening an ADODB connection in exclusive mode

Posted on 2000-04-13
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Last Modified: 2012-08-13
I need to open the database in exclusive mode so that I ensure consistent data.

I'm using an ADO connection to connect to the database.
if i give a con.mode=adModeShareExclusive just before opening the connection, i get an error.

Are there any restrictions in using this mode?

any clues as to why this happens?

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Question by:vidyas
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Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 2712079
What Provider/ODBC Driver do you use?
What database do you want to query?
What Error do you get?
Please post of your code!
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Expert Comment

by:detiege
ID: 2712133
Dim cnn1 As ADODB.Connection
   Dim rstTitles As ADODB.Recordset
   Dim strCnn As String

   ' Assign connection string to variable.
   strCnn = "Provider=sqloledb;" & _
      "Data Source=srv;Initial Catalog=pubs;User Id=sa;Password=; "

   ' Open connection and titles table.
   Set cnn1 = New ADODB.Connection
   cnn1.Mode = adModeShareExclusive
   cnn1.IsolationLevel = adXactIsolated
   cnn1.Open strCnn
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Expert Comment

by:wsh2
ID: 2713440
Deteige:
Very nice answer.. IF the questioner is using SQL as their server. As not all Provider's are created equal.. How do you know that SQL is the questioner's server of choice?.

As I find AngelIII's comment most germaine to the question, please change your answer to a comment.. until we know more.. <smile>.
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Author Comment

by:vidyas
ID: 2714712
The provider is the default: Microsoft OLE DB Provider

I want to query an Access database.

Code::

Public con As New ADODB.Connection '//The sole connection object
Public rs As New ADODB.Recordset
Public connectString As String

Public Function Initialize() As Boolean
'//This function initializes TracerInitVariables
'//when the application is invoked
'//for the first time

If Not TracerInit.IsDebugMode Then On Error GoTo errHandler

'//-connection set up
connectString = "DSN=Tracer"
con.Mode = adModeShareDenyWrite 'adModeShareExclusive
con.Open connectString
rs.CursorLocation = adUseClient
Initialize = True
Exit Function

errHandler:
    Call TracerError.ShowErr(Err)
    Initialize = False  '//-signal init failure
End Function
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Error returned::

The flow jumps to the label errHandler and displays a message "Errors occured".

and the return value of the function is false.
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Expert Comment

by:detiege
ID: 2714946
detiege changed the proposed answer to a comment
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Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 2714948
Unfortunately, you didn't tell us which version of Access, but i got the same error for A97 and A2K, so i think (need to look up doc) that this mode is not supported by ODBC driver for Access.

In the options of the ODBC DSN however i detected in the advanced part some interesting checkboxes which may resolve your problem...

FYI:
I suggest that you don't declare your variables AS NEW, as this is a performance break.
Instead declare AS and issue you SET = NEW statements in the Initialize Sub
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Author Comment

by:vidyas
ID: 2715038
oops.. forgot to mention the version.
it is Access 97.

pardon me, I couldn't find any checkboxes. could you please guide me where to find these options?

reg your suggestion:: thanks for the info and I'm gonna remove the 'new' from the declaration as per your suggestion, but i'd still like to know how this could affect the performance??
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LVL 142

Accepted Solution

by:
Guy Hengel [angelIII / a3] earned 50 total points
ID: 2715054
If you declare objects as new, on every line you use the object, VB will add code during compilation to check if the object is nothing and create the object if necessary.
I found the checkboxes when
*) i openend the ODBC applet in Control Panel
*) selected the DSN Trace
*) issue Configure
*) clicked on options button (these properties can also be found in the advanced screen)


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Author Comment

by:vidyas
ID: 2715279
guess what?? I don't get any kind of checkboxes.

What is the OS you are working on?

I'm on Win NT
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LVL 142

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 2715312
NT 4 SP 5 Access 97 MDAC 2.1
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Author Comment

by:vidyas
ID: 2715468
does this mean that i cannot open an access databse in exclusive mode?

if i can do this somehow, please let me know.
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Author Comment

by:vidyas
ID: 2715550
Thanks angelIII

I marked the database to be opened in Exclusive mode through control panel.
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