Teradata System State Changes
You can change the state of Teradata systems with unityadmin. The Teradata system state must be Active, Standby, or Read Only to start sessions on the Teradata system. The following table shows how to change Teradata system accessibility and Unity states.
| From |
To |
Commands |
| Active |
Standby |
SYSTEM DEMOTE
|
| Standby |
Active |
SYSTEM PROMOTE
|
To Active State Commands
The following table describes how to place a Teradata system or table in Active state from another state.
| To Active from |
Commands |
| Out of Service |
SYSTEM RECOVER
|
| Standby |
SYSTEM PROMOTE
|
| Read Only |
SYSTEM RECOVER
|
If a table is in a Restore state, it automatically goes into an Active state when recovery is complete.
From Active State Commands
From Active state, a Teradata system or table can be placed into the following states.
| From Active to |
Commands |
| Unrecoverable |
SYSTEM DEACTIVATE
|
| Out of Service |
SYSTEM HALT
|
| Read Only |
SYSTEM FREEZE
|
| Standby |
SYSTEM DEMOTE
|
From an Active state, a system is automatically placed in Restore state if the queue of pending Write requests is greater than the RecoveryQueueLimit parameter. This prevents the system from getting reads directed to it when it is far behind in writes, allowing the system time to catch up with the other systems in the cluster.