What is the purpose of the catalog command?
A. To review RMAN control file and recovery catalog metadata and ensure that its correct
B. To delete RMAN backup-related metadata from the recovery catalog
C. To create metadata in the control file and the recovery catalog related to backup set pieces
D. To create a report that lists database backups
E. To rebuild the recovery catalog
The catalog command is used to catalog backup set pieces or image copies in both the
control file and the recovery catalog so RMAN can use those backup set pieces or image copies.
原文：http://www.cnblogs.com/Babylon/p/7794381.html