connect sqlplus without tnsname.ora file .... 

sqlplus user/pass@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(Host=192.168.85.132)(Port=1521))(CONNECT_DATA=(SID=MYSID)))

sqlplus "user/pass@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(Host=192.168.85.132)(Port=1521))(CONNECT_DATA=(SID=MYSID)))"

sqlplus 'user/pass@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(Host=192.168.85.132)(Port=1521))(CONNECT_DATA=(SID=MYSID)))'


sqlplus 'sys/sys@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(Host=192.168.85.132)(Port=1521))(CONNECT_DATA=(SID=vihaan))) as sysdba'

ww
 sqlplus 'sys@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(Host=xxxx)(Port=1521))(CONNECT_DATA=(SID=rac2))) as sysdba'


 sqlplus /nolog


idle sqlplus> connect sys@'(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=xxxx)(PORT=1521)) (CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=RAC)))' as sysdba
Enter password:
Connected.