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Tuesday, July 14, 2009

Complete, Incomplete and Point-In-Time Recovery

Complete, Incomplete and Point-In-Time Recovery
July 15, 2009
Oracle Database, Backup, Recovery, TSPITR
  Complete recovery is recovering a database to the most recent point in time, without the loss of any committed transactions. Generally, the term "recovery" refers to complete recovery.
  Occasionally, however, you need to return a database to its state at a past point in time. For example, to undo the effect of a user error, such as dropping(RecycleBin)(Flash Database)(TSPITR) or deleting the contents of a table(Flash Table/LogMiner/Flash Transaction), you may want to return the database to its contents before the delete occurred. In incomplete recovery, also known as point-in-time recovery, the goal is to restore the database to its state at some previous target SCN or time.
  Point-in-time recovery is one possible response to a data loss caused by, for instance, a user error or logical corruption that goes unnoticed for some time. Point-in-time recovery is also your only option if you have to perform a recovery and discover that you are missing an archived log covering time between the backup you are restoring from and the target SCN for the recovery. Without the missing log, you have no record of the updates to your datafiles during that period. Your only choice is to recover the database from the point in time of the restored backup, as far as the unbroken series of archived logs permits, then perform an OPEN RESETLOGS and abandon all changes in or after the missing log. (If you discover that you have lost archived logs and your database is still up, you should do a full backup immediately.)

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