A session is a logical connection between the user and Teradata Database. A session permits a user to submit one transaction at a time and receive one response at a time, and the current session can have only one transaction outstanding at any time. A user may communicate through one or more active sessions concurrently.
A session is explicitly logged on and off from Teradata Database and is established when the Teradata Database server accepts the logon string of the user. When a session is logged off, the system discards the user-session identification and does not accept additional Teradata SQL statements from that session.
Request and Response Messages
When a session has been logged on, Teradata Database communicates with the host through request and response messages containing parcels of information. The maximum response message size limit is 1MB.
How Request Parcels Are Handled
To access Teradata Database from a mainframe client, the user or application program logs on through a Teradata client interface product and submits a request. The request is processed by the interface and directed to a TDP.
Each request is handled as follows:
The result of a query or a status becomes a returned answer set. The PE turns the answer sets for a request into one or more response parcels and returns them to: