INFO: ODBC Driver Must Be Thread Safe If Used with MTS (177411)

SUMMARY

An ODBC driver must be thread-safe if it is to be used by a Microsoft Transaction Server (MTS) component. MTS components transparently use an ODBC connection obtained from a pool of connections that is managed by the ODBC Driver Manager. This allows MTS to use a pool of connections that it can keep very busy, without the cost of opening and closing a connection for each component that accesses the database. Connections are used by a component and then returned to the pool.

Connections in the pool that have not been used for a set period of time will be freed, to minimize the use of server resources. The ODBC connection pool manager uses a worker thread to check for connections that have not been used for a certain amount of time. By default, the CPTimeout (connection pool timeout) value is 60 seconds, but you can change it if you want. Because this worker thread is different than the thread that opened the connection, the ODBC driver must be able to handle disconnect requests (SQLDisconnect) coming from a thread other than the thread that called SQLConnect. Some ODBC drivers cause a general protection fault (GPF) when the disconnect request is from a different thread.