Hi James Jeyaseelan,
You can add SAP_ALL into the profile who requires full access to BW system for admin users.
Use tcode RSECADMIN to create roles, authorization objects who requires BW system access.
Kindly refer to the following document which would be useful for you :-)
SAP Library - System Administration Tasks
Authorization in BI 7 - Part 1
https://scn.sap.com/thread/2085924
You need to enter the vale for auth object for required infoproviders, provide respective infoprovider name, for which someone needs access.
You need to create value of auth object and provide it's respective report name, create suitable role, add this auth object value into the role, add the role to BW login ID.
Let me know if these helps your query :-)
with Regards,
Antony Jerald.