Message Server

It is used to perform load balancing when more than one Application Server serving the same Group are Configured. It is also used to obtain the locks for Additional Application Server Processes.It is the First Process(server) to be started on a Hostname, IP address, Hardware Key(Customer key), Internal Port for Locking 3900, an External port for load balancing 3600 and HTTP port 8000(8100) etc.This log file is displayed in /usr/sap/SID/DVEBGMS00/work/dev_ms(AL11/ST11 Transaction) It is monitored by using SMMS. it displays the types of services configured on each Application Server(DIA, BTC, UPD, SPO, ICM) Enqueue Server and Message Server are installed together in a separate Instance with instance number from Netweaver 7.3 which is referred as ABAP SAP Central Service(ASCS)
Precisely Message Server is used for
  1. Login Load Balancing/Fail over(This is required only when more than one Application Server for the same purpose(group) are deployed).
  2. Obtaining Locks for Application Server Processes.(This is not Required from Net weaver 7.3 because all processes are establishing a direct TCP/IP Connection with Enqueue Process.
Logon Groups are defined in SMLG and RFC Server Groups are defined in RZ12.
Define a Logon Group in SMLG and assign to the Instances which are going to Participate in Load Balancing.
Configuring GUI
  1. Update /etc/hosts(hostname and IP Address)
  2. Update /etc/services(sapms<SID> 3600/tcp)
  3. Create a Logon Entry in GUI using the Option “Connection Type as Group Server Selection”
  4. Specify the Description, SID, name of the Message Server(Hostname:3600), Select the logon Group and save.
  5. The Least Loaded Server is calculated based on Algorithm(think time).
    Navigate to SMLG–>Menu GO TO-DIAGNOSIS–>Message Server Status Area–>The favorite Compute time/server is displayed.
Note: if Message Server is not Started then SAP System will be Down.
There will be only one Message Server in the Entire SAP SYSTEM.
The Message Server can be monitored by using ‘msmon’.

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