Should I run the Web Dispatcher as a standalone installation or as part of an ABAP or J2EE system?
We recommend installing the SAP Web Dispatcher as a separate system with a separate SID. The advantages are:
- Decouple the lifecycle of the SAP Web Dispatcher from the backend system. You can separately start/stop, upgrade and patch the Web Dispatcher without influencing the backend system and vice versa;
- You are free to serve multiple backend systems with a single SAP Web Dispatcher;
- Standalone installation is supported by the installation procedure (see this WIKI page and the SAP note 908097 - SAP Web Dispatcher: Release, Installation, Patches, Documentation);
- A separate SAP Web Dispatcher installation does not cost any more resources than an integrated setup.
On the other hand, there are reasons for an integrated setup of the SAP Web Dispatcher as part of a system:
- Running the SAP Web Dispatcher as part of an (A)SCS instance to participate in a high availability cluster setup. This is indeed the easiest way to make the SAP Web Dispatcher highly available. However, the same result can be achieved by installing a standalone SAP Web Dispatcher on the (A)SCS host and including it into the cluster setup as a separate failover entity. This should be possible as well, but the concrete implementation depends on the cluster product being used. For Microsoft cluster, see the SAP KBA 1564222 (How to install the SAP Web Dispatcher in a Microsoft Failover Cluster?);
- SAP Web Dispatcher can be managed together with the system: patching, starting, and stopping without additional effort.
The configuration to integrate a SAP Web Dispatcher into an (A)SCS instance is just a small addition to the (A)SCS instance profile (adding the relevant parameters, including the "Execute_XX" and "Start_Program_XX" parameters). Note that during the Rolling Kernel Switch (RKS) procedure the SAP Web Dispatcher inside the (A)SCS instance will be restarted, which interrupts currently outstanding requests.