新手求助-RMAN用sys用户连不上

RMAN用sys用户连不上，why？
[oracle@Redhat admin]$ rman target sys/ywang@ora10g nocatalog
Recovery Manager: Release 10.2.0.1.0 - Production on Mon Oct 4 23:51:21 2010
Copyright (c) 1982, 2005, Oracle.  All rights reserved.
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-00554: initialization of internal recovery manager package failed
RMAN-04005: error from target database:
ORA-01017: invalid username/password; logon denied
[oracle@Redhat admin]$ sqlplus
SQL*Plus: Release 10.2.0.1.0 - Production on Mon Oct 4 23:52:09 2010
Copyright (c) 1982, 2005, Oracle.  All rights reserved.
Enter user-name: sys
Enter password:
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
SQL>

用户名或者密码错误
请使用   rman  target /   试试