A database session is a logical connection between a CLIv2 application and the database. A session permits an application to send requests to, and receive associated responses from, the database. An application can establish any number of concurrent sessions.
A session is explicitly logged on and off. The session is established when the database accepts the user name and password of the user. The session is discarded when explicitly logged off by the application, when the application ends, when TDP is restarted, or when a TDP command ends the session.
Each session is identified to the application and to the database by a session number. A session number is assigned by TDP and is unique for a given TDP.