Excel VBA Query Using Access Database Hangs on 2nd Execute

[Mike Knight]

I have a MS Access 2003 Database named "AS400 Fields.mdb". This
database contains links to tables on an AS400.

In MS Excel 2003, I have VBA code that creates and executes queries
using the Access database, and returns the results to an Excel sheet.
There are many of these Excel query files and they all work at the
same time on different users' machines.

The first time the query is executed, results are returned to Excel in
usually less than 10 seconds. However, if the query is executed a
second time (without closing the Excel workbook), the code hangs at
the line surrounded by "=",s in the code below (this was tested with
message boxes). If the Excel file containing the VBA code is closed
and re-opened the code executes normally.

Is there a problem in my code? Am I doing something wrong?

Thanks,
Mike

Private Sub Execute_Query()
Dim X As Integer
Dim DB1 As ADODB.Connection
Dim RS1 As ADODB.Recordset
Const ConnectionStr As String =
"Provider=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source= Myserver Location Goes here\AS400 Fields.mdb"
Set DB1 = New ADODB.Connection
DB1.Open ConnectionStr

Set RS1 = New ADODB.Recordset
'=============================
RS1.Open QryStr, DB1
'=============================
'Copy the data
ActiveCell.Offset(1, 0).Select
ActiveCell.CopyFromRecordset RS1
RS1.Close
DB1.Close
Set RS1 = Nothing
Set DB1 = Nothing
End Sub

 

[Jamie Collins]

(e-mail address removed) (Mike Knight) wrote ...

I have a MS Access 2003 Database named "AS400 Fields.mdb". This
database contains links to tables on an AS400.

In MS Excel 2003, I have VBA code that creates and executes queries
using the Access database, and returns the results to an Excel sheet.
There are many of these Excel query files and they all work at the
same time on different users' machines.

The first time the query is executed, results are returned to Excel in
usually less than 10 seconds. However, if the query is executed a
second time (without closing the Excel workbook), the code hangs at
the line surrounded by "=",s in the code below (this was tested with
message boxes). If the Excel file containing the VBA code is closed
and re-opened the code executes normally.

Private Sub Execute_Query()
Dim X As Integer
Dim DB1 As ADODB.Connection
Dim RS1 As ADODB.Recordset
Const ConnectionStr As String =
"Provider=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source= Myserver Location Goes here\AS400 Fields.mdb"
Set DB1 = New ADODB.Connection
DB1.Open ConnectionStr

Set RS1 = New ADODB.Recordset
'=============================
RS1.Open QryStr, DB1
'=============================
'Copy the data
ActiveCell.Offset(1, 0).Select
ActiveCell.CopyFromRecordset RS1
RS1.Close
DB1.Close
Set RS1 = Nothing
Set DB1 = Nothing
End Sub

I can't think of a specific problem. I think you must isolate the
problem a bit more. What is QryStr e.g. a SELECT query, a stored
procedure? Have you tried doing something else with the Connection
object e.g. use its Execute method to UPDATE or INSERT to a test
table, rather than return a row set? Have you tried running a
different query/stored proc to return a different result set? Have you
tried keeping the connection open for the second call? (this may not
be an option in production if you have many workbooks connecting to
the .mdb)

Jamie.

--

 

[Mike Knight]

(e-mail address removed) (Mike Knight) wrote ...


I can't think of a specific problem. I think you must isolate the
problem a bit more. What is QryStr e.g. a SELECT query, a stored
procedure? Have you tried doing something else with the Connection
object e.g. use its Execute method to UPDATE or INSERT to a test
table, rather than return a row set? Have you tried running a
different query/stored proc to return a different result set? Have you
tried keeping the connection open for the second call? (this may not
be an option in production if you have many workbooks connecting to
the .mdb)

Jamie.

--

Jamie

Qrystr is a string variable containing my select statement.

I just tried the Execute method:
(Set RS1 = DB1.Execute(QryStr, , adCmdText))

Different queries using different AS400 Files (linked tables in Access
DB) have the same problems.

I will experiment with leaving the connection open.

Thanks for your reply.

Mike

 

[Jamie Collins]

(e-mail address removed) (Mike Knight) wrote ...

I will experiment with leaving the connection open.

Something else to try might be to execute multiple times in a VBA
module the .mdb when open in the MS Access UI, using the
CurrentProject.Connection object (which AFAIK is an 'always connected'
connection). I'm wondering if Excel is disconnecting to the .mdb but
the .mdb connection to the AS400 remains open and locked in some way.

Jamie.

--

 

[Mike Knight]

(e-mail address removed) (Mike Knight) wrote ...


Something else to try might be to execute multiple times in a VBA
module the .mdb when open in the MS Access UI, using the
CurrentProject.Connection object (which AFAIK is an 'always connected'
connection). I'm wondering if Excel is disconnecting to the .mdb but
the .mdb connection to the AS400 remains open and locked in some way.

Jamie.

--

Jamie,

Are you saying that I should try opening the Access file from Access
before executing a query?

The AS400 connection does not seem to be the problem. We
simultaneously executed the same Excel query (opened read only) on two
different machines. One of the machines would not execute the query a
second time, but the other one would. The one that would, at other
times, would not. Since both Excels were using the same Access
database, I don't believe the AS400 was locked.

I wonder if this is a "memory leak" problem - somewhat similar to the
Microsoft article 319998 concerning Excel sheets? I modified my code
to create a new instance of Excel as per article 246335, but the
problem still occurs. If I manually close the instance of Excel that
ran the VBA, manually open another instance, and re-run the VBA, no
problem seems to occur.

The reason I use Access is as follows. In Excel 97, DAO3.5, I could
connect directly to the AS400 and use VBA functions to manipulate and
"clean-up" AS400 data (padded spaces, convert decimals, etc.) for use
in Excel. After upgrading to Excel 2003, DAO3.6, the ability to
connect directly and use the functions seemed to go away for the most
part. Also, I could never get satisfactory results connecting with
ADO. Using ADO and Access 2003 as a go-between restored complete use
of VBA functions. Basically, Excel VBA writes the SQL for an Access
query.

Mike

 

[Jamie Collins]

(e-mail address removed) (Mike Knight) wrote ...

Are you saying that I should try opening the Access file from Access
before executing a query?

The AS400 connection does not seem to be the problem. We
simultaneously executed the same Excel query (opened read only) on two
different machines. One of the machines would not execute the query a
second time, but the other one would. The one that would, at other
times, would not. Since both Excels were using the same Access
database, I don't believe the AS400 was locked.

I wonder if this is a "memory leak" problem - somewhat similar to the
Microsoft article 319998 concerning Excel sheets? I modified my code
to create a new instance of Excel as per article 246335, but the
problem still occurs. If I manually close the instance of Excel that
ran the VBA, manually open another instance, and re-run the VBA, no
problem seems to occur.

Just a suggestion to try and isolate the source of the problem i.e. is
it the connection from Excel to the.mdb or the connection from .mdb to
the AS400 (might be worth checking the lock file for the lock file).

Ideally your code should be able to recover from a connection failure.
Review your ADO timeout properties and consider sinking your
connection/recordset objects in a class module and taking advantage of
asynchronous connection/processing. This may not help if you are
correct about Excel hanging.

Jamie.

--

 

[TK]

Hi Mike:

Let me add a couple more suggestions

I put some error handling in your procedure and a connection
test. The procedure did not fail as tested on this computer but perhaps
a procedure on a different computer may have a glitch and the error
handler should fail it..

Is there a need to declare the connection string as Const. It could cause
problems if declared out of the procedure.

One other consideration I have found is if none of your procedures calls
the Access repair and compact utility the DB can get huge and slow..
If you are not familiar with the utility it’s Access Tools/DataBase Utilites/
Compact and Repair.

If you check the file size in explorer before and after you see if it was
necessary.

Private Sub Execute_Query()

On Error GoTo ErrHandler

Dim X As Integer

Dim DB1 As ADODB.Connection
Dim RS1 As ADODB.Recordset

'Is there a need to declare this as a Const if it
'gets declared outside of the procedure you have form scope

Const ConnectionStr As String = "Provider=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source= Myserver Location Goes here\AS400 Fields.mdb"
'I prefer
Dim Connections As String
ConnectionStr = "Provider=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source= Myserver Location Goes here\AS400 Fields.mdb"

Set DB1 = New ADODB.Connection
DB1.Open ConnectionStr

'Test to see if we are connected
If DB1.State = adStateOpen Then
MsgBox "Welcome to! "
Else
MsgBox "No Data today."
End If

Set RS1 = New ADODB.Recordset
'=============================
RS1.Open strSQL, DB1
'=============================
'Copy the data
ActiveCell.Offset(1, 0).Select
ActiveCell.CopyFromRecordset RS1

RS1.Close
DB1.Close

'Test to see if we are still connected
If DB1.State = adStateOpen Then
MsgBox "Welcome to! "
Else
MsgBox "Where Closed!"
End If

Set RS1 = Nothing
Set DB1 = Nothing

Exit Sub

ErrHandler:
MsgBox "Sorry, an error occured. " & Err.Description, vbOKOnly

End Sub

Good Luck
TK

 

[Jamie Collins]

Another thought: perhaps some of the table's properties that relate to
the link could be refreshed e.g.

How To Use ADO to Refresh/Create Linked Table for Password Secured Jet
4.0 Database:
http://support.microsoft.com/default.aspx?scid=kb;en-us;240222&Product=ado

Microsoft Jet 4.0 Provider Properties:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnacc2k/html/adoproperties.asp

Jamie.

--

 

[Mike Knight]

Hi Mike:

Let me add a couple more suggestions

I put some error handling in your procedure and a connection
test. The procedure did not fail as tested on this computer but perhaps
a procedure on a different computer may have a glitch and the error
handler should fail it..

Is there a need to declare the connection string as Const. It could cause
problems if declared out of the procedure.

One other consideration I have found is if none of your procedures calls
the Access repair and compact utility the DB can get huge and slow..
If you are not familiar with the utility it’s Access Tools/DataBase Utilites/
Compact and Repair.

If you check the file size in explorer before and after you see if it was
necessary.

Private Sub Execute_Query()

On Error GoTo ErrHandler

Dim X As Integer

Dim DB1 As ADODB.Connection
Dim RS1 As ADODB.Recordset

'Is there a need to declare this as a Const if it
'gets declared outside of the procedure you have form scope

Const ConnectionStr As String = "Provider=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source= Myserver Location Goes here\AS400 Fields.mdb"
'I prefer
Dim Connections As String
ConnectionStr = "Provider=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source= Myserver Location Goes here\AS400 Fields.mdb"

Set DB1 = New ADODB.Connection
DB1.Open ConnectionStr

'Test to see if we are connected
If DB1.State = adStateOpen Then
MsgBox "Welcome to! "
Else
MsgBox "No Data today."
End If

Set RS1 = New ADODB.Recordset
'=============================
RS1.Open strSQL, DB1
'=============================
'Copy the data
ActiveCell.Offset(1, 0).Select
ActiveCell.CopyFromRecordset RS1

RS1.Close
DB1.Close

'Test to see if we are still connected
If DB1.State = adStateOpen Then
MsgBox "Welcome to! "
Else
MsgBox "Where Closed!"
End If

Set RS1 = Nothing
Set DB1 = Nothing

Exit Sub

ErrHandler:
MsgBox "Sorry, an error occured. " & Err.Description, vbOKOnly

End Sub

Good Luck
TK

TK,

Sorry I'm so late in responding - accounting period end activities got
in the way!

First, the database is compacted and has remained at 16,488KB - no
data is actually stored from Excel queries in the Access database -
only linked tables to the AS400.

Second, I removed the code declaring the connection string as a
constant, DIMed the variable, and set it equal to the provider + data
source.

Third, I added the Msgbox statements and the error checking.

Fourth, the file was saved on the server and Excel closed.

I have two computers side by side, both connected to the server.

On computer 1, I opened Excel and the file, ran the changed code and
the messages were displayed: "Welcome to" and "Where Closed" (after
data was returned). Without closing Excel or the file, I re-ran the
program and got the message "Welcome to". No data or error was
returned after an appropriate time - the hour-glass was displayed. I
did not stop the code (this can't be done with control break), but
left Excel and the file "running".

On computer 2, I opened read-only the same file as on computer 1 from
the server location (only after computer1 hung-up). I ran the code
and received the same results as were received the first time the code
was run on computer 1, within seconds. The code on computer 2 was
executed again and the computer "hung-up".

Note that both computers were executing the same code from the same
server file, and that both computers were using the same Access
Database on the server. It doesn't appear that an AS400 connection
problem within Access exists - computer 2 was able to use the DB even
while Computer 1 was using it. Both computers are Intel Pentium 4
2.66GH 248MB Windows XP SP1 Office 2003.

Thanks for your input - any suggestions are appreciated.

Mike