Question

Roll forward and roll back are two major ways of backup. Which among the following should be logged for facilitating roll forward?

• A. After images
• B. Before images
• C. All valid transactions
• D. None of these

Answer 1

The correct option is A After images

Roll forward and roll back are two major ways of backup. After images should be logged for facilitating roll forward.

In some situations, it may be necessary to undo, or reverse the effects of a transaction. This is called "rolling back." When recovering a database, it may be necessary to redo, or replay the effects of a transaction. This is called "rolling forward."

The reconstructing of data is achieved through media recovery, which refers to the various operations involved in restoring, rolling forward, and rolling back a back up of database files.