FIX: Memory Leak in Microsoft Access ODBC Driver in MDAC 2.0 (195017)

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This bug was corrected in in a newer version of the Access ODBCDriver included with MDAC 2.1.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);
   }
   *****