Unable to pass characters in Web PL/SQl procedure when calling from URL

Could you please help me here. I have created one procedure with IN Varchar2 parameters, default NULL. I want to invoke that procedure from URL and able to do that that.

I tried calling below scenarios: 1. URL without any parameter - Worked 2. URL with Parameter as ?uid=12345 - Worked 3. but when calling with alphabets like ?uid=ADMIN - Failed and unexpected message displays with no details.

I tired passing 'Admin', "Admin" but no luck .

Can you please suggest how to pass character/alphabets in my case.

Thanks for your time and reply,

Subroto