Wednesday, March 7, 2012

SAP Web Dispatcher

The SAP Web dispatcher is used for ‘Load Balancing” and as a “Software Web Switch”, in a SAP system with several SAP NetWeaver Application Servers for Web applications. It lies between the Internet and SAP system in the DMZ. It is the entry point for HTTP(S) requests into the SAP system, which consists of one or more Web application servers. As a "software Web switch", the SAP Web dispatcher can reject or accept HTTP connections. When it accepts a connection, it balances the load to ensure an even distribution across the servers.

Planning : Sizing a SAP WEB DispatcherMemory usage for internal tables
-> Server tables
->> Holding information about connected servers
->> Usually very small (90 kBdefault, few MB for very large system)
-> Connection tables
->> Holding information about the open connections
->> concurrent_conn= (users * req_per_dialog_step*conn_keepalive_sec)/ (thinktime_per_diastep_sec)
->> mpi/total_size_mb= (concurrent_conn* mpi_buffer_size)/(1024* 1024)
->>> Default: mpi_buffer_size= 32kB
->>> Default: mpi/total_size_mb= 500
->End to End SSL table
->>1.8 MB for 10.000 entries

Installation StepsMedia for the web dispatcher is provided with the J2EE kernel:

1.Download kernel files from SAP service market place

2.Extract kernel using
$ mkdir /tmp/sapwebdisp
$ cp dw_??_########.SAR /tmp/sapwebdisp
$ cd /tmp/sapwebdisp
$ sapcar –xvf dw_??_########.SAR (disp+work Package)

3.Copy the sapwebdisp and icmadmin.SAR files to a directory on what is to be the Web Dispatcher host.
$ mkdir /usr/sap/sapwebdisp
$ cp /tmp/sapwebdisp/sapwebdisp /usr/sap/sapwebdisp/.
$ cp /tmp/sapwebdisp/icmadmin.SAR /usr/sap/sapwebdisp/.

4.Extract the icmadmin.SAR file into that directory using the command
$ sapcar –xvf icmadmin.SAR

5.Generate an initial profile for the Web Dispatcher by running the command
$ ./sapwebdisp –bootstrap

6.Start the web dispatcher with
$ cd /usr/sap/sapwebdisp
$ ./sapwebdisp pf=sapwebdisp.pfl –auto_restart

Profile ParametersThese are the most basic profile parameters

->>Must be unique on the host and must be in the range between 0 –98
->>Used to distinguish shared memory segments of different SAP WebDispatchers on the same host
->>Hostname of the host where the message server is running (in case of double stack installation the ABAP MS has to be used)
->>Port of the message server
->>Time to refresh internal routing tables
->>protocol and port where the dispatcher is listening for incoming requests
->>Configuration of admin access

link :

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