I have created Oracle 11gR2 in Windows. I can do tnsping db from other machines. I can login to from toad and sqlplus with user abc/abc@db1.

But I can not login with sys from toad and sqlplus. It says permission denied.

1) Let me know what could be the issue?
2) Does application servers need to have 11g client to connect to 11gR2 db through application? It gives invalid username/password error while logging with abc/abc@db1