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Q229100: PRB: VFP ODBC Driver Cannot Be Used With ODBC Connection Pooling

Article: Q229100
Product(s): Microsoft FoxPro
Version(s): 2.5,3.0,3.0b,5.0,5.0a,6.0
Operating System(s): 
Keyword(s): kbDatabase kbODBC kbvfp300 kbvfp300b kbvfp500 kbvfp500a kbvfp600 kbODBC351 kbGrpDSFox k
Last Modified: 26-OCT-2000

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b, 5.0, 5.0a, 6.0 
- Microsoft Data Access Components version 2.5 
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SYMPTOMS
========

If connection pooling is enabled for the following ODBC drivers:

- Microsoft Visual FoxPro Driver
- Microsoft FoxPro VFP Driver (*.dbf)
- Microsoft dBase VFP Driver (*.dbf)

The following error may occur:

  "Exception occurred within ODBC driver <driver name> during disconnect
  operation, likely not thread-safe ..."

CAUSE
=====

The ODBC manager requires that all ODBC drivers that use Connection Pooling be
threadsafe. Despite the entry in the help file, the Visual FoxPro ODBC driver
(Vfpodbc.dll) is not a threadsafe ODBC driver.

RESOLUTION
==========

Do not enable connection pooling for the Visual FoxPro driver.

STATUS
======

This behavior is by design.

MORE INFORMATION
================

To ensure that connection pooling is not enabled for the Visual FoxPro ODBC
driver, check the Microsoft FoxPro VFP Driver (*.dbf) and the Microsoft Visual
FoxPro Driver entry in the Connection Pooling tab of the ODBC Control Panel.
Both of these entries should say <not pooled>.

For the ODBC 3.5 Driver Manager, connection pooling is controlled on a driver by
driver basis through the CPTimeout registry setting. If the setting is not
present, or if it is set to <not pooled>, connection pooling is disabled
for that driver. Other valid entries will be a string value that specifies the
timeout in seconds.

For the ODBC 3.0 Driver Manager, connection pooling is enabled by default, and
cannot be disabled through the registry.

The connection pooling setting is kept in a registry entry for each ODBC driver.
The following registry key is created by default when installing the Visual
FoxPro ODBC driver:

HKEY_LOCAL_MACHINE\Software\ODBC\ODBCINST.INI\<driver name>\[CPTimeout]

Where <driver name> is Microsoft FoxPro VFP Driver (*.dbf), Microsoft
Visual FoxPro Driver, and Microsoft dBase VFP Driver (*.dbf).

REFERENCES
==========

Microsoft Developer Network; search on: "Microsoft Transaction Server FAQ:
Databases and Transactions"; topic: "ODBC Connection Pooling"

Additional query words:

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Keywords          : kbDatabase kbODBC kbvfp300 kbvfp300b kbvfp500 kbvfp500a kbvfp600 kbODBC351 kbGrpDSFox kbDSupport kbMDAC250 
Technology        : kbVFPsearch kbAudDeveloper kbMDACSearch kbMDAC250 kbVFP300 kbVFP300b kbVFP500 kbVFP600 kbVFP500a
Version           : :2.5,3.0,3.0b,5.0,5.0a,6.0
Issue type        : kbprb

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