In the DB Access Module for MySQL, 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 MySQL connection structure.

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