To confirm that the agent is communicating properly to the controller, you can use the following methods:

Check if data is being written to the agent log in /logs. This indicates that the agent is able to send metrics and events to the controller.You can also look for any errors or warnings in the log file that might indicate a connection issue1

Select Application > Tiers and Nodes > Look for the Node. This shows you the list of nodes that are registered with the controller and their status.You can see if the node is up or down, the agent version, the last reported time, and the machine name2

According to the Cisco AppDynamics Associate Administrator Certification document1, one of the topics covered in the exam is ''Monitor agent performance and connectivity''.To do this, you need to ensure that the application agent can communicate with the controller, which may require SSL configuration if the controller is using SSL2.You also need to check that there are enough licenses available on the controller for the application agent to register and report data3. If the agent is using the wrong application name or does not have enough memory, it may not start at all or may crash, which are different problems from not being able to connect to the controller.Reference:

Cisco AppDynamics Associate Administrator Certification

Configure SSL for the Controller and the App Server Agent

License Rules and Restrictions

Database Visibility provides metrics on the performance of your database and helps troubleshoot performance-related issues. Database Visibility consists of four main components: Database Agent, Collector, Controller, and Events Service (on-premises only). The Database Agent is a standalone Java program that collects performance metrics about your database instances and database servers. The Collector is the process that runs within the Database Agent to collect performance metrics about your database instances and database servers. The Controller is the central interface where you can see all your database instances and database server performance metrics. The Events Service stores high volumes of metric data.

According to theOverview of Database Visibility, the following types of information are sent to the Controller:

Database-level metrics, such as the number of queries processed and other database statistics

Names and attributes of all sessions, clients, queries, and other objects on the monitored system

The following types of information are sent to the Events Service:

Time that each query spends at each wait state

Individual query statistics for databases that support it

Information about individual execution plans in databases that support it

Therefore,B(Average Number of Slow Connections) andC(Top Leaked Connections) are two stats that are available in Database Visibility.Reference:

Cisco AppDynamics Associate Administrator Certification

Overview of Database Visibility - AppDynamics

Database Visibility - AppDynamics

Percentile metrics are a way to measure the distribution of response times for a Business Transaction. They show the value below which a certain percentage of measurements fall. For example, the 50th percentile metric shows the median response time, and the 99th percentile metric shows the worst-case response time for 99% of the transactions. To enable percentile metrics, you need to go to Configuration > Slow Transaction Thresholds and indicate 5 whole numbers between 1 and 99 as Percentiles to Collect. You can then view the percentile metrics in the Metric Browser under Business Transaction Performance > Business Transactions > <Application Name> > <Business Transaction Name> > Percentiles.

https://docs.appdynamics.com/display/PRO45X/Percentile+Metrics

The Policy Test Bench gives administrators the ability to test and debug policy execution. It allows you to simulate events and see how the policies and actions respond to them.You can also view the policy execution logs and troubleshoot any issues1Reference:1: Policy Test Bench