Final answer:
Performing db recovery depends on the length of downtime and recovery time.
Step-by-step explanation:
The correct answer is d) Downtime; Recovery Time; Database Schema.
Performing a database recovery is necessary when the downtime (the period during which the database is unavailable) is longer than the recovery time (the time it takes to restore the database to a consistent state). Database recovery involves modifying the database schema to restore it to its previous state.
For example, let's say you have a backup of your database and you need to recover it after a failure. If the downtime required to perform the recovery is shorter than your acceptable recovery time, you can proceed with the recovery. However, if the downtime is longer than your acceptable recovery time, it may not be feasible to perform the recovery.