执行 duplicate target databaseto orcl from active database nofilenamecheck报错如下：
RMAN> duplicate target databaseto orcl from active database nofilenamecheck; Starting Duplicate Db at 23-DEC-15
using target database control file instead of recovery catalog
allocated channel: ORA_AUX_DISK_1
channel ORA_AUX_DISK_1: SID=19 device type=DISK
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of Duplicate Db command at 12/23/201510:57:12
RMAN-05541: no archived logs found in target database
出现这种错误很可能是你刚刚将主数据库切换为归档模式然后紧接着就利用RMAN的duplicate创建standby数据库导致的。原因就在于主数据库切换为归档模式之后还未发生过切换，手动在主数据库上切换一次就可以了
SYS@orcl>alter system switch logfile;