RMAN 备份出现：RMAN-20021: database not set RMAN> backup full database format '/opt/Oracle/backup/backup_%T_%s_%p.bak';Starting backup at 01-SEP-11 using channel ORA_DISK_1 RMAN-00571: ===========================================================RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============RMAN-00571: ===========================================================RMAN-03002: failure of backup command at 09/01/2011 00:30:19 RMAN-20021: database not set RMAN-06031: could not translate database keyword原因是在另一个窗口将数据库由mount改到open操作引起的：SQL> ALTER DATABASE OPEN;此时，RMAN未接获数据库打开的通知，，退出，再从新连入即可解决。
（如果不行尝试设置nls_lang，其实应该不用的）