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Complete and Incomplete Media Recovery

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Media recovery updates a backup to either to the current or to a specified noncurrent time. When performing media recovery, you can recover the whole database, a tablespace, or a datafile. In any case, you always use a restored backup to perform the recovery.

Learn Oracle - Highlights

Learn Oracle - Complete Recovery

Complete recovery involves using redo data or incremental backups combined with a backup of a database, tablespace, or datafile to update it to the most current point in time. It is called complete because Oracle applies all of the redo changes contained in the archived and online logs to the backup. Typically, you perform complete media recovery after a media failure damages datafiles or the control file.

You can perform complete recovery on a database, tablespace, or datafile. If you are performing complete recovery on the whole database, then whether you are using RMAN or SQL*Plus you must:

  • Mount the database
  • Ensure that all datafiles you want to recover are online
  • Restore a backup of the whole database or the files you want to recover
  • Apply online or archived redo logs, or a combination of the two
If you are performing complete recovery on a tablespace or datafile, then you must:

  • Take the tablespace or datafile to be recovered offline if the database is open
  • Restore a backup of the datafiles you want to recover
  • Apply online or archived redo logs, or a combination of the two

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Learn Oracle - Incomplete Recovery

Incomplete recovery uses a backup to produce a noncurrent version of the database. In other words, you do not apply all of the redo records generated after the most recent backup. You usually perform incomplete recovery of the whole database in the following situations:

You can perform complete recovery on a database, tablespace, or datafile. If you are performing complete recovery on the whole database, then whether you are using RMAN or SQL*Plus you must:

  • Media failure destroys some or all of the online redo logs.
  • A user error causes data loss, for example, a user inadvertently drops a table.
  • You cannot perform complete recovery because an archived redo log is missing.
  • You lose your current control file and must use a backup control file to open the database.
To perform incomplete media recovery, you must restore all datafiles from backups created prior to the time to which you want to recover and then open the database with the RESETLOGS option when recovery completes. The RESETLOGS operation creates a new incarnation of the database--in other words, a database with a new stream of log sequence numbers starting with log sequence 1.

Learn Oracle - Tablespace Point-in-Time

The tablespace point-in-time recovery (TSPITR) feature enables you to recover one or more tablespaces to a point-in-time that is different from the rest of the database. TSPITR is most useful when you want to:
  • Recover from an erroneous drop or truncate table operation
  • Recover a table that has become logically corrupted
  • Recover from an incorrect batch job or other DML statement that has affected only a subset of the database
  • Recover one independent schema to a point different from the rest of a physical database (in cases where there are multiple independent schemas in separate tablespaces of one physical database)
  • Recover a tablespace on a very large database (VLDB) rather than restore the whole database from a backup and perform a complete database roll-forward

Learn Oracle -Media Recovery Options

Because you are not completely recovering the database to the most current time, you must tell Oracle when to terminate recovery. You can perform the following types of media recovery.

Type of Recovery Function
Time-based recovery Recovers the data up to a specified point in time.
Cancel-based recovery Recovers until you issue the CANCEL statement (not available when using Recovery Manager).
Change-based recovery Recovers until the specified SCN.
Log sequence recovery Recovers until the specified log sequence number (only available when using Recovery Manager).




We learned Complete and incomplete recovery . Next we will move to RMAN and User Managed backups.
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