Application performance monitoring 

No, it is not possible to use RUM monitor without injecting script in the webpage.

The size of the agent will be minimal and will vary based on the agent type. For example, a Java agent will be around 10MB in size. You can also check the agent's load on the application using this link.
https://www.manageengine.com/products/applications_manager/help/apm-insight-java-agent-performance-report.html

You can modify the Apdex calculation by modifying the 'Apdex Threshold' in APM Insight agent configuration. Kindly refer to this help to know more. Based on your Application response time requirement, consult with your application team and make an informed decision.

The calculation does not consider 75 samples out of 100 samples. It just takes the response time of each transaction and takes the Apdex threshold value and based on these parameters it is finding whether the transaction is satisfied or tolerating or frustrated. You can see the sample calculation in this page.
https://www.manageengine.com/products/applications_manager/help/apdex-score.html

There is only one agent for monitoring the application performance that is APM Insight. APM Insight feature is available in standalone Applications Manager as well as the APM Plugin inside the OpMagager.
https://www.manageengine.com/products/applications_manager/help/java-transaction-monitoring.html
You can refer this page to understand the metrics collected by APM Insight monitoring.
https://www.manageengine.com/products/applications_manager/help/apm-insight-dashboard.html

You can find the detailed illustration of satisfied, frustrated, tolerated percentage in this page.
https://www.manageengine.com/products/applications_manager/help/apdex-score.html

As of now, we do not have the option to ingest information from third party tools into the APM Insight monitor.

You can find the list of applications and DBs that are supported by APMInsight monitor in this page.
https://www.manageengine.com/products/applications_manager/help/apm-insight-java-agent-app-servers-supported.html

Yes, we do. Please contact our support to get the detailed information.

Yes, the OpManager agent will be used for server monitoring, whereas, APM Insight agent will be added to the application server for application performance monitoring.

You can make use of service templates to monitor specific services on a Windows server VM. https://www.manageengine.com/products/applications_manager/help/service-templates.html

The Apdex metric and other metric data are stored based on the retention period set in Applications Manager, which can be set under Settings → Performance Polling → APM Insight.

Our application performance monitoring tool collects information on web transactions and non-web transactions (background tasks) and typically produces performance data automatically. To avoid any potential overhead, we do instrumentation on critical packages only. However, for additional monitoring needs, you have the option to implement custom instrumentation. This enables you to track interactions that might not be automatically captured by Applications Manager, providing a way to identify critical issues by adding specific details to your transactions.

APM Insight is one of the monitors in APM module and it needs an add-on in your license. You can verify if you have the add-on from Settings → Product License. If you do not have it and looking for trial, please reach out to appmanager-support@manageengine.com

The agents can be deployed on Linux OS as well to monitor your applications hosted there. Based on the type of application, you can deploy the agent accordingly.

Application and Server performance will not be impacted by the Agent. We have tested the applications and calculated the Agent Overhead report.
https://www.manageengine.com/products/applications_manager/help/apm-insight-java-agent-performance-report.html

OpManager Plus is an integrated solution that streamlines the process of IT operations management thereby eliminating the need for multiple monitoring tools. This holistic tool provides greater visibility across your IT infrastructure by combining the network and application performance monitoring capabilities within a single console. If you go with OpManager Plus with APM add-on, then managing OpManager and Applications Manager standalone deployments will not be needed.

APM Insight gives you visibility into the way your applications behave for your end users. You can get comprehensive end-to-end transaction awareness across your entire infrastructure, enabling you to isolate performance issues and resolve them quickly without degrading the performance of your applications. Yes, application-specific agents are deployed into the servers where your applications will be hosted. https://www.manageengine.com/products/applications_manager/help/apminsight-working.html

Apart from the host server that's hosting the application, servers on which the application is running is called as instance in APM Insight.

The automated setup of APM Insight is supported from Applications Manager v172100 onwards.

APM and Netflow Analysis are distinct monitoring approaches. APM injects custom instrumentation code into your web application to track transactions and code behavior, providing granular insights. Conversely, Netflow Analysis focuses on network traffic patterns, collecting aggregated data from network devices to offer a broader view of network health and potential bottlenecks. While both can be used for application monitoring, APM offers detailed application-specific data, while Netflow Analysis provides network-level insights. Combining both can offer a comprehensive understanding of application performance by correlating application metrics with network conditions.

Yes, you can collect custom data from a method invocation by deploying the APM Insight agent for the compatible applications in your organization. Learn more

No, vulnerability assessment cannot be performed for applications in Applications Manager.