Besides securing the GIS services, which we learned in the previous chapter, it is important to keep an eye on the services to verify that they are healthy and available for use. Monitoring a live system is crucial to maintaining stability and performance; not only to avoid potential failures but even for debugging and tracing back an event. That is why having a system record its activities results in a rich database of logs that can be used for investigation. Logfiles tell a fascinating story to those who can read it. They carry the history of all events narrated in thorough detail. ArcGIS for Server, like any other system, keeps logfiles for all events, from the basic "connection established" event to the severe "service failed to initiate" event. In this chapter, we will learn how to read logfiles and understand them in order to extract useful information that can help solving problems that might occur.