Relevant Model/Business Object (AFC) for tracking Performance Management (rating/evaluation)

Summary:
Which model/business object to use to create Transaction control for tracking Performance Management (rating, evaluation) etc.?

Content (please ensure you mask any confidential information):
As part of a client requirement, we would want to create a custom control to detect users who have the ability to update both performance ratings and salaries. While we are able to monitor activities related to salary, we are unable to do that for performance rating as we are having difficulty to identify the correct business object. Though there is one business object related to Audit-performance measure, but, the attributes are not addressing our requirement. Upon checking with the client, we observed that they have the audit trail enabled for an object called "Performance Evaluations", but, we could not