Online transaction recovery is automatically invoked by a Teradata system restart and includes the following processes:
- Rolling back transactions that were not completed at the time of the crash or restart
- Completing transactions that were committed
Changes made to underlying data by transactions are recorded in the Transient Journal (TJ). AMPs keep track of transactions in progress using the TJ which is stored on each AMP’s disk.
| IF... | THEN... |
|---|---|
| all the modification operations successfully complete on all the AMPs working on behalf of the transaction | that transaction is successful and there is no further concern for recovery of that transaction. |
| a transaction does not complete due to a Teradata system crash or forced restart | those transactions are backed out as part of the Teradata system recovery process when the Teradata system restarts. |