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Recovery - Point-in-Time Recovery

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• Recovery - Point-in-Time Recovery
  • Point-in-time Recovery
  • Terminology
  • Specifying the Recovery Point in Time

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Point-in-time Recovery

• Point-in-time Recovery

• Benefits:

  • Quick recovery of one or more objects to an earlier time, without affecting the state of the other tablespaces and objects in the database.
  • No effect on other objects

• Recovery scope:

  • Database point-in-time recovery (DBPITR)(incomplete recovery):
    • To recover of an entire database to a specified past target time, SCN, or log sequence number
    • To migrate a database to a different platform by creating a new database on the destination platform and performing a transport of all the user tablespaces, but excluding the SYSTEM tablespace
  • Tablespace point-in-time recovery (TSPITR):
    • To recover one or more contained tablespaces to an earlier point in time
  • Table point-in-time recovery (TPITR):
    • To recover one or more tables or table partitions to an earlier point in time

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Terminology

• Target time:
  • The point in time or SCN that an object will be recovered to
• Recovery set:
  • data files composing the tablespaces to be recovered
• Auxiliary set:
  • Required data files that are not part of the recovery set. It typically includes:
    • A copy of SYSTEM tablespace
    • Data files that contain undo segments from the target instance
    • In some cases, a temporary tablespace, used during the export of database objects from the auxiliary instance
• Auxiliary destination:
  • A location on disk that can be used to store any of the auxiliary set data files, control files, and online logs of the auxiliary instance during PITR.
  • Files stored in the auxiliary destination can be deleted after PITR is complete.

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Specifying the Recovery Point in Time

• Specify Point in Time by:
  • UNTIL SCN integer:
    • system change number (SCN)
    • The SCN is an upper, noninclusive limit.
  • UNTIL TIME 'date string':
    • The time inthe date format:
      • Of the NLS_LANG and NLS_DATE_FORMAT environment variables,
      • Date constants
        • e.g., SYSDATE -5 = 5 days earlier than the system date
  • UNTIL SEQUENCE integer (THREAD integer):
    • The log sequence number and thread number
    • RMAN selects only files that it can use to restore or recover up to but not including the specified sequence number.

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