Using NWBC with a Load Balancer
The information in this topic applies only to the NWBC connection type.
If a load balancer is available within the network, it can be used directly with NWBC. Instead of configuring a direct URL on a specific application server, change the URL that NWBC is configured to, to use the load balancer. On startup, NWBC triggers a first HTTP request to the load balancer, which then redirects to an application server. For the duration of the NWBC session, the load balancer only communicates with this specific application server. All applications that are started run on the assigned application server. (This is similar to a typical SAP GUI session that stays on the same assigned application server and starts all new windows on the same server.)
In NWBC for Desktop, navigation data is cached on an ABAP system (AS ABAP), and not on a specific application server. Therefore, if the load balancer assigns a different application server the next time NWBC for Desktop is started, the cached data are not invalidated.
We highly recommended that you use SAP Web Dispatcher as a load balancer, since it contains key information about HTTP traffic that can be used to route all subsequent HTTP requests more effectively to the same application server.
By default, transaction NWBC starts NWBC for HTML or the ~launch page on the same AS ABAP application server. However, transaction NWBC also includes all available information about an external Web Dispatcher, or message server used as load balancer if configured in the HTTPURLLOC table. In the HTTPURLLOC table, configure an entry for application = /NWBC/* to influence the URL generation of NWBC. By consequence, the startup URL is changed to reference the configured load balancer directly.
You can also define load balancing settings in an SAP Logon/SAP GUI system connection, and refer this connection in the SAP GUI Logon Description of the NWBC connection. For more information about defining load balancing settings for transactions running in remote systems, see the topic Configuring Special SAP GUI System Connection Properties for Remote Systems.
SAP Note
1040325 
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HTTP load balancing: Message Server or Web Dispatcher