What is authorization Objects,Profile and Role?
Actions and the access to data are protected by authorization objects in the SAP system. Authorization objects allow complex checks that involve multiple conditions that allow a user to perform an action. The conditions are specified in authorization fields for the authorization objects and are AND linked for the check. Authorization objects and their fields have descriptive and technical names.
Authorization objects in the SAP system
An authorization is always associated with exactly one authorization object and contains the value for the fields for the authorization object. An authorization is a permission to perform a certain action in the SAP system. The action is defined on the basis of the values for the individual fields of an authorization object.
A role is primarily a functional description
The technical realization of the role, in the form of concrete authorizations is achieved through the authorization profile associated with the role.
What is a composite profile?
A set of profiles which are included under a single profile name is called as a composite profile (SU02)
How can you find missing authorizations? How can you solve?
By running the SU53 transaction.
Identify the authorization object where the required filed value is to be given and the do the same thru SU01 or PFCG.
Also See: High Level & Fundamental understandings of SAP System Architecture