why Oracle 12c has introduced two new roles – AUDIT_ADMIN and AUDIT_VIEWER

why Oracle 12c has introduced two new roles – AUDIT_ADMIN and AUDIT_VIEWER. Include a discussion of what database auditing is and what it does. Consider why these new roles were introduced and what problem they are meant to resolve. Do not simply define the roles. Explain why they are useful. 

Cite your sources in-line and at the end. Provide a URL for your citations.  Write in essay format not in bulleted, numbered or other list format. Do not copy without providing proper attribution.