| 摘要 |
A database rollback processor allows rollback, or rewind, of the data and metadata to a point at which a failover or other metadata change occurred, therefore "rewinding" the metadata to a previous consistent point. The rollback processor identifies transaction entries in a redo log resulting in changes to the metadata. The changes are identified backward to a target recovery time. Transactions affecting the metadata are stored in a stack. The transactions are then backed out of the metadata according to the stack to restore the metadata to the state at the target recovery time. Data changes from the redo log may then be applied to the corresponding metadata as it existed at the target recovery time. Since the target recovery time is not bound by the timing of the snapshots, but rather may be at an arbitrary point chosen as the target recovery time, a failover, replication or recovery operation need not rely on the snapshot time. |
