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. 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.
When an instance is started, the dispatcher process attempts to establish a connection to the message server so that it can announce the services it provides (DIA, BTC, SPO, UPD, etc.). If this does not work, an appropriate entry is made in the system log.
If the messages server stops working, it must be restarted as quickly as possible, to ensure system continues to operate trouble-free.
The following section explains how to administrate, test and monitor the message server.
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.
You have different options to monitor and test the message server.
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.
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 parameter ms/server_port_<xx>).
For more information see Monitoring the Message Server Using the Browser.
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.
· The Monitoring Program msmon provides the same functions as transaction SMMS in the SAP System.
· You can use the Test Program lgtst to check the connection to the message server, and to display the active instances and logon groups that the message server can currently see.
· With program msprot you can monitor the message server. The program issues continuously the status of the application servers logged on the message server, and is stopped if the message server is stopped. You will be notified of the termination of the message server and can respond to this.
You can make communication to the message server more secure by setting a few profile parameters. For more information, see Security Settings for the SAP Message Server.