The task of the message server is to inform all the servers (instances) belonging to an SAP System of the existence of the other servers. It can also be contacted by other clients (for example, SAPlogon, RFC clients with load balancing) to get information about load balancing.
The SAP Message Server runs as a separate process mostly on the same host as the central instance.
Only one message server can run on each SAP System.
If the messages server stops working, it must be restarted as quickly as possible, to ensure system continues to operate trouble-free.
Monitoring the Message Server in the SAP System
To monitor the message server, you can use the Message Server Monitor (transaction SMMS) in the SAP System. You can check and change all the important settings, create and view traces, read statistics, and so on.
Monitoring the Message Server from the Browser
You can display details of the servers and logon groups from the Web browser too. To do this, in the URL use the host of the message server and the HTTP port of the message server (profile parameterms/server_port_<xx>).
Monitoring and Testing the Message Server at Operating System Level
To monitor the message server at operating system level you need access to the host on which the message server is running. You can log on here with user <sid>adm.
At operating system level there are various programs available, which are delivered with the standard system.
You will usually find the test programs in the executable directory /usr/sap/<SID>/SYS/exe/run.