[oracle@data ~]$ echo $ORACLE_SID
ORCL
[oracle@data ~]$ sqlplsus orcl_user@ORCL
-bash: sqlplsus: command not found
[oracle@data ~]$ sqlplus orcl_user@ORCL
SQL*Plus: Release 10.2.0.1.0 - Production on Wed Oct 17 09:29:16 2007
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Enter password:
ERROR:
ORA-12154: TNS:could not resolve the connect identifier specified
Enter user-name:
[oracle@data ~]$ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.1.0 - Production on Wed Oct 17 09:29:46 2007
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to an idle instance.
SQL>
SQL> exit
Disconnected
[oracle@data ~]$