Immediate update Method :
Database may be updated by some operations of a transaction before the transaction reaches its commit point.
These operations are typically recorded in the log on disk by force writing before applied
If a transaction fail after recording some change to the database, but before commit point, the effect of its operations on the database must be undone (transaction must be rollback)
Need both undo and redo in recovery .Immediate update is known as “UNDO/REDO Algorithm”to the database.
If fail occurs .The executing (active) transaction at the time of failure may have recorded some Changes in the database. The effect must be undone.
Answer : Immediate updates as a recovery protocol is preferable, when : Writes are more than reads .
