A.Global indexes are rebuilt automatically at the end of the DDL operation thereby avoiding problems with the UNUSABLE status.
B.You do not have to search for invalid global indexes after the DDL command completes and rebuild them individually.
C.Global indexes are maintained during the operation of the DDL command and therefore can be used by any concurrent query.
D.Global indexes remain intact and available for use by data manipulation language (DML) statements even for sessions that have not enabled the skipping of unusable indexes.