备份归档日志后删除3天前日志

RMAN> run {
2>     allocate channel t1 type disk;
3>     backup tablespace MMSG
4>     format 'archive_%s_%p_%u'
5>     (archivelog all );
6>     delete noprompt archivelog until time "sysdate -3";
7>     release channel t1;
8>    }