Every monitoring tool makes one foundational choice: install software on each server, or reach in from outside using standard protocols. Both work. They fail differently, cost differently and see differently.
ManageEngine Applications Manager is primarily an agentless tool for server and database monitoring - it collects data over WMI, SSH and SNMP without installing anything on your servers. Other tools lead with an agent on every machine. Before choosing, understand what each model genuinely gives and takes away - marketing on both sides leaves half of this out.
Depth versus footprint. Neither side is free.
The monitoring server logs in remotely on a schedule and asks standard questions: WMI queries on Windows, commands over SSH on Linux, SNMP reads on devices that support it. Setup is minutes per server - an account, the right permissions, an open management path. That is why agentless tools spread so well in offices: your fiftieth server is as easy as your first, and there is nothing extra running on production machines for anyone to object to.
An agent lives on the server, watches continuously, can push alerts the second something happens, and can collect detail no remote protocol offers - per-process histories, log events as they occur, and in APM's case, code-level transaction traces (the APM Insight agent for Java and .NET in the ManageEngine world). The bill arrives as work: deploying agents, keeping them updated, fixing the occasional broken one, and reassuring every security review that asks why this software is on every server.
For server health, database checks and availability - the daily bread of a small or mid-size office - agentless is the right default: fast to roll out, nothing to maintain per server, more than deep enough. Add agents surgically, only where the extra depth pays: the one critical application whose slow transactions you must trace into the code, or a machine whose logs you must never miss. "Agentless everywhere, agent where it earns" beats both purist positions.
Agentless: use a dedicated monitoring account, scope its rights to what collection needs, and rotate its password like any privileged credential - a leaked monitoring login is a map of your whole network. Agent-based: treat agent updates like patching, because an unpatched agent is itself software running with high privileges on every server. The model changes; the discipline does not.
See the full live demo - adding servers, reading the dashboard and setting alerts, step by step.
▶️ Watch Full VideoFor the metrics it collects - CPU, memory, disk, service and database health - no; it reads the same counters an agent reads. It is less continuous: data arrives in polling intervals rather than as a live stream.
Because code-level tracing is a different job. Knowing the application is slow is agentless work; knowing which method inside the code is slow needs an agent inside the process. Most offices need the first; development-heavy teams need both.
Yes, and it is common: agentless for infrastructure health across everything, plus an agent on the one or two servers running the critical application. Just avoid collecting the same metric twice into two alert streams.