奇怪的錯誤！

奇怪的錯誤：
C:\Documents and Settings\ibsadmin>sqlplus
businessdata_dr3/businessdata_dr3@aora

SQL*Plus: Release 10.2.0.1.0 - Production on Fri Jul 20 19:13:21 2012

Copyright (c) 1982, 2005, Oracle.  All rights reserved.

ERROR:
ORA-12154: TNS:could not resolve the connect identifier specified

Enter user-name: system/system

Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options

SQL> conn businessdata_dr3/businessdata_dr3@aora
Connected.
SQL>
再來一次：
SQL> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64
bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

C:\Documents and Settings\ibsadmin>sqlplus
businessdata_dr3/businessdata_dr3@aor
a\

SQL*Plus: Release 10.2.0.1.0 - Production on Fri Jul 20 19:14:44 2012

Copyright (c) 1982, 2005, Oracle.  All rights reserved.

ERROR:
ORA-12154: TNS:could not resolve the connect identifier specified

Enter user-name: system/system@aora

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> conn businessdata_dr3/businessdata_dr3@aora
Connected.
SQL>