What is the purpose of establishing business priorities? What are the advantages

What is the purpose of establishing business priorities? What are the advantages of this process?
Explain, with an example, how if the facility, department, or business process disaster recovery charts of responsibilities are lacking vital information at this stage, it could affect the overall effectiveness of the disaster recovery plan.
Book Reference:
GUIDE TO DISASTER RECOVERY
ERBSCHLOE, MICHAEL
ISBN13: 9780619131227
EDITION: 1ST
FORMAT: PAPERBACK