Each session is logged on and off via calls to CLIv2 routines or through ODBC or JDBC, which offer a one-step logon-connect function.
Sessions are internally managed by dividing the session control functions into a series of single small steps that are executed in sequence to implement multithreaded tasking. This provides concurrent processing of multiple logon and logoff events, which can be any combination of individual users, and one or more concurrent sessions established by one or more users and applications.
Once connected and active, a session can be viewed as a work stream consisting of a series of requests between the client and server.
You can establish session pools, in which an application logs on to Teradata Database and establishes a pooled connection, so users can use application functions that access the database without the need to log on individually. This capability is particularly advantageous for transaction processing in which interaction with Teradata Database consists of many single, short transactions.
Teradata Database identifies a session with a session number, the username of the initiating (application) user, and the logical host identification number of the connection TDP.
On a mainframe client, use the ENABLE SESSION RESERVE command from Teradata Director Program to reserve session capacity in the event of a PE failure. To release reserved session capacity, use the DISABLE SESSION RESERVE command.
The major functions of session control are session logon and logoff.
Upon receiving a session request, the logon function verifies authorization and returns a yes or no response to the client.
The logoff function terminates any ongoing activity and deletes the session context.
Applications that use connection pooling can be configured to use trusted sessions, asserting individual end user identities and roles to manage privileges and audit access.
Requests and Responses
Requests are sent to a server to initiate an action. Responses are sent by a server to reflect the results of that action. Both requests and responses are associated with an established session.
A request consists of the following components:
- One or more Teradata SQL statements
- Control information
- Optional USING data
If any operation specified by an initiating request fails, the request is backed out, along with any change that was made to the database. In this case, a failure response is returned to the application.
For more information about:
- SESSION RESERVE, see Teradata Director Program Reference.
- Trusted sessions, see Security Administration, B035-1100.