Doubt about message server

[AtulKumarJain]

Hello ,

Today I have gone through SAP document  and stuck at  defination of message serevr

"Message Server (MS) handles communication between the distributed dispatchers within the AS ABAP, thereby enabling scalability of several

    parallel application servers. The message server is configured only one per SAP system"

So As above statement tell MS is used between communication between diffrent dispatcher .

Suppose if I have only one instce (central instance )  so in this case what is job of message server.?

Because there is only one dispather so message server not requird here?

Please clarify this.

Do not post any lik or thread .I have searched in scn but didnt find suitable answer

BR

Atul

[Former Member · Accepted solution]

There would still be a message server in a single-instance system. It just doesn't have a lot to do as everything happens on that one instance so no load-balancing is required.

You can't have an SAP system without a message server. The system architecture requires it.

Steve.

[Former Member · Accepted solution]

It also makes sense to have message server based logins even if there is only one application server to start with. That way you are anticipating for growth and once there is need to add another application server, no changes will be required on the client side.

[Former Member · Accepted solution]

Indeed. As I said, you don't actually have a choice, but because every system has a message server it means that you can start with a single system instance and add extra capacity very easily - just install new dialog instances and start them up as required.

One thing it is helpful to do, though, is to create a logon group, even though strictly not necessary for a single system instance, and have everyone login through that. Then, if you do ever add extra instances they get automatically used without having to change everyone's login mechanism. We didn't think of this until it was too late, and making the change for 800 users using a variety of different software distribution mechanisms for SAPgui was more work than it should have been!

After a recent hardware upgrade we're now back to a single system production instance after previously need three lower power machines, but we've stuck with the logon group so that we can scale up again should we ever need to.

Steve.

[Former Member]

Hi Atul,

I am tempted to post this link hoping it helps.

http://help.sap.com/saphelp_nw04/helpdata/en/40/c235c15ab7468bb31599cc759179ef/content.htm

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.

Best Regards,

Anita