At the client site I got the following error:
C:\Documents and Settings\oliver field>RMAN target sys@xxx
Recovery Manager: Release 10.2.0.4.0 - Production on Wed Aug 17 17:36:20 2011
Copyright (c) 1982, 2007, Oracle. All rights reserved.
target database Password:
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-12154: TNS:could not resolve the connect identifier specified
To successfully connect via RMAN I had to open RMAN with 3 separate commands (MOUNT DATABASE FIRST):
C:\Documents and Settings\oliver field>SET ORACLE_SID=xxx
C:\Documents and Settings\oliver field>RMAN
RMAN> CONNECT TARGET SYS