ISQL login error SYBASE

Hi Guys,

We recently installed SAP NW7.3 Ehp1 on Windows 2008 server with Sybase database version 15.7,installation was successful without any error's,when I try to login to database its throw error

I logged in as SIDADm and exeuted below command and end up with below error,

D:\sybase\SBP\OCS-15_0\bin>isql

Password:

CT-LIBRARY error:

ct_connect(): directory service layer: internal directory control layer

error: Requested server name not found.

Could any one help me out with how this can be fixed?

Regards

Uday