The exact definition of the service levels and their measurement is the first thing that the IS auditor should review in order to understand the problem of different opinions on the availability of their application servers.
Service levels are the agreed-upon standards or targets for delivering IT services, such as availability, reliability, performance, and security. Service level measurement is the process of collecting, analyzing, and reporting data related to the achievement of service levels. By reviewing the exact definition of the service levels and their measurement, the IS auditor can identify any gaps, inconsistencies, or ambiguities that may cause confusion or disagreement among IT and the business. The other options are not as important as reviewing the exact definition of the service levels and their measurement, as they do not address the root cause of the problem. References: CISA Review Manual, 27th Edition, page 372