Explanation/Reference:
Explanation:
Overview of Block Media Recovery (link)
Purpose of Block Media Recovery
You can use block media recovery to recover one or more corrupt data blocks within a data file. Block media recovery provides the following advantages over data file media recovery:
Lowers the mean time to recover (MTTR) because only blocks needing recovery are restored and

recovered
Enables affected data files to remain online during recovery

Without block media recovery, if even a single block is corrupt, then you must take the data file offline and restore a backup of the data file. You must apply all redo generated for the data file after the backup was created. The entire file is unavailable until media recovery completes. With block media recovery, only the blocks actually being recovered are unavailable during the recovery.
Block media recovery is most useful for physical corruption problems that involve a small, well-known number of blocks. Block-level data loss usually results from intermittent, random I/O errors that do not cause widespread data loss, and memory corruptions that are written to disk. Block media recovery is not intended for cases where the extent of data loss or corruption is unknown and the entire data file requires recovery. In such cases, data file media recovery is the best solution.