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.
答案：（B、C、E）
解析：
A（X），不是必须，也可以使用控制文件来记录备份和恢复的信息。
D（X），