12.3 What Are the Recovery Options?
There are many different ways in which a database can be recovered:
As a snapshot in time (from export or file-level backups without archive logging enabled)
To a point in time (from file-level backups plus archive logs)
Until cancel (from file-level backups plus archive logs)
For an entire tablespace, you can restore one or more datafiles from file-level backups. From an export, you can restore an entire schema, a table, or a set of tables. Using the import option "INDEXFILE=<file_name>", you can obtain a script to build an index or set of indexes from an export file.
Backup and Recovery Reminders
Here are a few reminders about the behavior of different types of backup and recovery.
Cold file-level backups performed for Oracle7 or Oracle8 databases without the Recovery Manager, and backup sets created using the Oracle8 Recovery Manager without archivelog mode enabled, allow recovery of tablespaces or the entire database to the point in time when the backup was made. If a backup was made on Monday at 1:00 A.M. and the recovery was performed on Thursday, all data entries, DDL statements, and other modifications to the database done from 1:00 A.M. Monday morning until Thursday, when the recovery was required, would be lost.
Cold file-level backups, hot backups, backup sets, and full image copies, with archivelog mode enabled, enable recovery to be performed to a point in time or until cancel. If a backup was made on Monday at 1:00 A.M. and the recovery was desired to Thursday at 2:00 P.M., the database recovery can be performed to the time desired, as long as archive logging is enabled and the archive logs are available.
Exports enable the recovery of individual tables or groups of tables but can only be performed to recover to the point in time at which the export was done. Exports are only a snapshot in time. You cannot use archive logs with an export to recover to a point in time beyond the time when the export was performed.
There are two types of database recovery:
12.3.1 Online Recovery
For an online recovery from within the database, use the commands RECOVER TABLESPACE... and/or RECOVER DATAFILE... in tablespace recovery. From outside of the database, use the import utility to recover tables, schemas, or the entire database from an export file.
12.3.2 Offline Recovery
From an offline recovery from SQLDBA or the Server Manager line mode option ( svrmgrl ) with the database mounted but not opened, you can recover the system tablespace as well as an entire database. Using this method, if a tablespace has been corrupted and the DBA is absolutely sure that the tablespace can be rebuilt, the datafiles associated with that tablespace can be altered with the OFFLINE DROP option and the database opened. In such a case, the tablespace will be "untouchable" and must be dropped immediately. Use great caution when applying this technique, and contact Oracle World-Wide Support before proceeding with this plan since there are possible repercussions that could result in still more severe database corruption.