The two resources that are best for monitoring potential server issues are CPU usage and memory usage. CPU usage is the percentage of time that the processor (CPU) of the server is busy executing instructions or processes. CPU usage indicates how much workload the server can handle and how fast it can process requests. High CPU usage may affect the performance or availability of the server and cause delays or errors. Memory usage is the amount of physical memory (RAM) or virtual memory (swap space) that the server uses to store data or run applications. Memory usage indicates how much space the server has to store temporary or intermediate data or results. High memory usage may affect the performance or availability of the server and cause swapping or paging. The other options are either not relevant or not direct indicators of server health. For example, user connections are the number of users who are connected to a database server at any given time; firewall usage is the amount of data that passes through a firewall device or software; index usage is the frequency or efficiency of using indexes on tables to speed up queries; query execution is the process of running SQL statements on a database server. References: CompTIA DataSys+ Course Outline, Domain 3.0 Database Management and Maintenance, Objective 3.2 Given a scenario, monitor database performance.