Availability is one of the three basic functions of security management that are present in all systems. Availability is the assertion that a computer system is available or accessible by an authorized user whenever it is needed. Systems have high order of availability to ensure that the system operates as expected when needed1. Availability provides building of fault tolerance system in the products. It also ensures the backup processing by including hot and cold sites in the disaster recovery planning1.
Having a local user database option to ensure the application can still be used if the corporate directory is not responsive to login requests is an example of availability, as it ensures that the users can access the application even if the primary authentication service is unavailable. This is a form of backup processing that provides an alternative means of accessing the application in case of a failure or outage. Having a local user database option does not affect the access, authorization, or auditing of the application, as these are related to the identification, verification, and monitoring of the users, not the availability of the application. Reference: Availability in Information Security - GeeksforGeeks; 5 Security Concepts Every Developer Should Understand; The 7 Basic Principles of IT Security - Techopedia.