In the DB Access Module for PostgreSQL, the database callbacks preEnvAllocate and postEnvAllocate are invoked during the construction of the RWDBDatabase object. The callback preEnvDestroy is invoked while destroying the RWDBDatabase object. The connection callbacks are invoked with respect to the allocation, deallocation, connect and disconnect of the PostgreSQL connection handle PGconn.

The Access Module for PostgreSQL allocates the connection handle and connects using a single vendor call PQconnectdb. Hence, the callbacks preConnAllocate, postConnAllocate and preConnect are invoked before calling PQconnectdb. Callback postConnect is invoked after the call to PQconnectdb.

The DB Access Module for PostgreSQL disconnects and deallocates the connection handle in a single vendor call PQfinish(). Hence, both callbacks preDisconnect() and preConnDestroy() are invoked before the call to PQfinish(). Please refer to the DB Interface Module User's Guide for more information.