The sessions in a pool are logged on to the Teradata Database once using the START POOL operator command (for details see Chapter 7: “TDP Commands”) and remain logged on until they are explicitly logged off by the STOP POOL (or STOP POOL and LOGOFF POOL) operator commands.
When a pool is first established, all pool sessions are not in use. When an application sends a logon request whose logon string matches that of the session pool, as described below, the application is assigned an available session from the pool. This results in a “quick” logon, because the application’s logon request does not have to be sent to the Teradata Database.
The session assigned to the application is marked “in‑use” and cannot be reassigned to another application until the current application logs off. The logoff returns the session to the pool, where it becomes available for use by another application.