A. A virtual private catalog owner can create a local stored script, and have read/write access to a global stored script.
B. The virtual private catalog owner cannot create and modify the stored scripts.
C. The set of views and synonyms that make up the virtual private catalog is stored in the schema of the RMAN recovery catalog owner.
D. To perform most of the RMAN operations, the virtual catalog owner must have the SYSDBA or SYSOPER privilege on the target database

A. It must be used because all RMAN-related backup and recovery metadata information is contained in it.
B. It provides a convenient， optional， repository of backup- and recovery-related metadata.
C. It provides the ability to store RMAN scripts for global use by any database that has access to the repository.
D. It provides a means of storing all RMAN backup sets physically in an Oracle database server. 
E. It provides the ability to store backup records for more than a year.