The general sequence of a Teradata Database system recovery is as follows:
- The status of each transaction on each online AMP is determined by the Teradata Database system.
All of the online AMPs at the time of the restart work together to determine which transactions were complete, and which ones were not completed. Completed transactions are ignored and incomplete ones are backed out. The process of rolling back incomplete transactions might take some time.
Write and exclusive locks are set against all data modified by incomplete transaction.
- All locks needed for the recovery are set, and the Teradata Database system begins roll back or completion of the transactions.
- The Teradata Database system accepts work and is operational. If new transactions reference the inconsistent data of to-be-rolled-back transactions, they are blocked until the recovery process restores the data and releases the lock.
- Down AMP recovery begins.