FIX: Memory Leak with ODBC Driver Manager During Connection

The information in this article applies to:

• Microsoft Open Database Connectivity, version 1.0

SYMPTOMS

When an ODBC application makes a sequence of calls to connect to an ODBC driver, a memory loss of the order of a few hundred bytes may occur. The loss of memory depends on the actual driver in use and the exact calls being made.

CAUSE

The sequence of calls that exhibit this behavior are:

   SQLAllocEnv
   SQLAllocConnect
   SQLConnect or SQLDriverConnect
   SQLDisconnect
   SQLFreeConnect
   SQLFreeEnv

For Microsoft Access and Microsoft Visual Basic for Windows applications, the behavior is exhibited when a new connection to an ODBC driver is made to either access attached tables or to create a dynaset or a snapshot.

When using Microsoft FoxPro Connectivity Kit, the problem is encountered on a call to DBConnect(). Microsoft Foundation Classes (MFC) users will see the problem when CDatabase::Open and CrecordSet::Open are called.

For Microsoft Word for Windows users, this behavior will be exhibited when connecting to an ODBC data source using Microsoft Query. This includes use of the INSERT DATABASE and MAIL MERGE functionality in Microsoft Word.

WORKAROUND

For those drivers that return SQL_SUCCESS_WITH_INFO on SQLDriverConnect or SQLConnect call, an application can work around this problem by calling SQLError call to retrieve the error message that is cached in Driver Manager; therefore, freeing up the memory. The SQLError can be called immediately after SQLConnect or SQLDriverConnect returns SQL_SUCCESS_WITH_INFO, calling SQLError repeatedly, until it returns SQL_NO_DATA_FOUND.

An example of an ODBC Driver that normally returns SQL_SUCCESS_WITH_INFO on a successful connection is SQL Server Driver.

STATUS

Microsoft has confirmed this to be a problem in ODBC Driver Manager version 1.0. This problem was fixed in the version 2.x ODBC Driver Manager. Contact your primary support provider for more information.