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Q195017: FIX: Memory Leak in Microsoft Access ODBC Driver in MDAC 2.0

Article: Q195017
Product(s): Open Database Connectivity (ODBC)
Version(s): WINDOWS:2.0,2.1 SP2,2.5,3.5
Operating System(s): 
Keyword(s): kbDatabase kbDriver kbJET kbMDAC kbODBC kbSDKDataAc200bug kbGrpDSMDAC kbDSupport kbMDAC
Last Modified: 12-JUN-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft ODBC Driver for Access, version 3.5 
- Microsoft Data Access Components versions 2.0, 2.1 SP2, 2.5 
-------------------------------------------------------------------------------

SYMPTOMS
========

The Microsoft Access ODBC Driver, version 3.51.1713, which is provided with the
Microsoft Data Access Components version 2.0, leaks memory when opening a
connection, performing a query on that connection, and then closing the
connection.

RESOLUTION
==========

To work around this behavior, keep the connection open as long as possible.
Minimizing the number of times you make a connection will minimize the memory
leak.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

This bug was corrected in in a newer version of the Access ODBC Driver included
with MDAC 2.1.

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

As an example, the following code causes several hundred bytes to leak for each
iteration through the loop:

     *****
     for(int nLoops=0; nLoops < 1000; nLoops++)
     {
       RETCODE rc;
       SQLAllocEnv(&henv);
       SQLAllocConnect(henv, &hdbc);

       SWORD nResult;
       UCHAR szConnectOutput[255];
       rc = SQLDriverConnect(hdbc, NULL,(UCHAR*)(const char*)"DSN=MYDSN",
                          SQL_NTS,szConnectOutput, 255, &nResult,
                          SQL_DRIVER_COMPLETE);

       SQLAllocStmt(hdbc, &hstmt);
       rc = SQLExecDirect(hstmt, (UCHAR *)"SELECT * from table1", SQL_NTS);

       SQLFreeStmt(hstmt,SQL_DROP);
       SQLDisconnect(hdbc);
       SQLFreeConnect(hdbc);
       SQLFreeEnv(henv);
     }
     *****

Additional query words:

======================================================================
Keywords          : kbDatabase kbDriver kbJET kbMDAC kbODBC kbSDKDataAc200bug kbGrpDSMDAC kbDSupport kbMDAC250 
Technology        : kbAudDeveloper kbAccessSearch kbODBCSearch kbMDACSearch kbMDAC200 kbMDAC210SP2 kbMDAC250 kbODBCAccess350
Version           : WINDOWS:2.0,2.1 SP2,2.5,3.5
Issue type        : kbbug
Solution Type     : kbfix

=============================================================================

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