SAP Web Application Server support high availability through the technique called switchover. The installation, configuration, and testing procedures are documented to provide readers with step-by-step guidelines in building an overall highly-available system with DB2 and SAP. There's an intro, and resource page, which contains links to related whitepapers and websites. Or you can go directly to the PDF that describes the integration of DB2 Universal Database, SAP R/3 Enterprise 4.70, and Sun Cluster 3.1 on the Solaris 9 environment.