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Thursday, August 8, 2019

What is backward database recovery?

What is backward database recovery?

  • Where after-images are applied to the database
  • Switching to an existing copy of the database
  • Where after-images and before-images are applied
  • Where before-images are applied to the database 
What is backward database recovery?


 Backward Recovery. Backward recovery restores a journaled database to a prior state. Backward processing starts by rolling back updates to a checkpoint (specified by -SINCE or -AFTER) prior to the desired state and replaying database updates forward till the desired state.

Backward Recovery uses "BEFORE_IMAGE" journaling. With BEFORE_IMAGE journaling, GT.M captures the database updates, as well as "snapshots" of portions of the database immediately prior to the change caused by the update. Unlike forward recovery which works on a backup database, backward recovery works only on  production (current) database provided it is usable and BEFORE_IMAGE journaling is enabled.




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