Database Administration Questions

Redo logs are logical and physical structures that are designed to hold all the changes made to a database and are intended to aid in the recovery of a database.

ALTER INDEX <index_name> REBUILD;

To perform one of these function on an index, table, or cluster:

 - To collect statistics about object used by the optimizer and store them in the data dictionary. 

 - To delete statistics about the object used by object from the data dictionary.

 - To validate the structure of the object.

 - To identify migrated and chained rows off the table or cluster.

A distributed database is a network of databases managed by multiple database servers that appears to a user as single logical database. The data of all databases in the distributed database can be simultaneously accessed and modified.

Complete database recovery from disk failure is possible only in ARCHIVELOG mode. Online database backup is possible only in ARCHIVELOG mode.