| Oracle recovery allows one to restore physical | | | | 'surviving instance' automatically puts into use redo logs |
| backup and re-construct it, and then give it to Oracle | | | | to get back committed data files in database 'buffers' |
| Server. Recovering restored data file means updating | | | | that was gone when instance failed. Oracle discards all |
| it utilizing 'redo records', that are, records of alternations | | | | transactions in progress on failed instance, and clears |
| made to database after backup was obtained. If one | | | | out locks put on crashed instance. The major tool for |
| puts into use Recovery Manager, he can recover | | | | 'oracle recovery' is recovery manager, which is |
| restored data files with 'incremental backup', which is | | | | actually a CLI (line interface) that directs Oracle server |
| actually a data file that contains only altered data | | | | processor to recover, restore and backup database. |
| blocks. | | | | Crash recovery comes about when either single |
| Oracle carries out instance recovery and crash | | | | instance database breaks down, or all instances of |
| recovery automatically after any instance failure. | | | | 'multi instance database' crash. In this recovery type, an |
| Instance failure basically involves two basic operations; | | | | instance first opens database and executes certain |
| first forward backup to a current time through online | | | | recovery operations. Unlike instance and crash |
| 'redo records' and second, rolling changes back in | | | | recovery, media recovery type is executed on users |
| uncommitted transaction to original state. | | | | command. In this type, users make use of archived |
| Instance recovery occurs in open database, when an | | | | re-do logs and incremental backup to make 'restored |
| instance finds out that another one has crashed. The | | | | backup' or to revise it to specific time. |