When a Teradata system or table is in a Standby state, it only receives writes to keep current as long as there is another active copy. No reads are sent to a Teradata Database system or table in Standby unless no active Teradata system or table is available.
When demoting a system or table to a Standby state, all in-flight reads are complete and any new reads are rerouted to another Teradata system.
When a Teradata Database system is in Standby state, all tables on that system become Standby.