Unity has the ability to sustain long planned outages without taking applications offline. This ability can be used in situations from short outages for simple maintenance work or restarts to longer outages for Teradata system expansions, upgrades, or full replacements.
Unity tracks the Teradata system state which can be changed to control access to the system. The system state is employed for passive and managed routing. Using the HALT operation, you can close down and stop all sessions on a Teradata system. If a user routing rule allows the sessions to fail over to the second system, the sessions can fail over when the system becomes out of service. Unity recovery of managed sessions is the second mechanism that allows Teradata systems to be re-synced automatically.
Unity can manage outages on three levels – the entire system, a database, or an individual table.