Hi Shashank,
Yes, I do have an idea. This is not something you execute. This is something you set in your SETTINGS .dxc configuration file that this specific DSA is using as a parameter.
e.g. If you want to set attributes called 'telephoneNumber' and 'eMail' to be unique, you would:
set unique-attrs = telephoneNumber, email;
Once done, restart the DSA and after that if you try to add duplicate value for any of those two that might have already been assigned to an existing user, it will be denied and the add or modify operation will fail.
Hope this helps.
Thanks,
Hitesh