There are several ways of monitoring an SAP system. The simplest is just to check the ports on which the corresponding SAP services are running. Normally these are TCP ports 3200/3300 for system number
00, 3201/3301 for system number
01 etc. This can be done with the generic plugin described in 6.7.1 Testing TCP ports, page 132. But it is possible that no user is able to log in even though the port is reachable, because SAP-internal services fail, making it impossible to work with the system.
To really test the complex interaction of various SAP components, you require a program that communicates on an application layer with the SAP system. There are two alternatives here: the more simple one uses the program ...