Originally posted by akhadar
one more point is take care that the parameter
SQLNET.AUTHENTICATION_SERVICES= (NTS) in SQLNET.ORA is not commented out or 'NTS' is not replaced with NONE.
it would have errored with Insufficent Privilages and not TNS Protocol Adapter error.

If I have two databases on the same server, how do I connect / as sysdba in SQL*Plus?
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C:\>set ORACLE_SID=SIL

C:\>SQLPLUS /NOLOG

SQL*Plus: Release 8.1.7.0.0 - Production on Mon Apr 14 20:34:24 2003

(c) Copyright 2000 Oracle Corporation. All rights reserved.

SQL> CONNECT / AS SYSDBA
ERROR:
ORA-12560: TNSrotocol adapter error
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Post this...coz some times windows sucks....and will not set ur SID that u wished to.
Code:
C:\>set oracle_sid=oemrep

C:\>echo %oracle_sid%
oemrep