MDAC 2.5 SDK - ODBC Programmer's Reference
Chapter 16: Interoperability
Some drivers and DBMSs limit the number of statements and connections that can be active at one time. These numbers can be as small as one. For more information, see the SQL_MAX_CONCURRENT_ACTIVITIES and SQL_MAX_DRIVER_CONNECTIONS options in the SQLGetInfo function description, and "Statement Handles" and "Connection Handles" in Chapter 4, "ODBC Fundamentals."