SAP Application Servers and SAP clients communicate with the SAP Primary Application Server (PAS) using the name of the server where the PAS Instance is running. Likewise, the SAP PAS communicates with the Database (DB) using the name of the DB server. In a high availability (HA) environment, the PAS may be running on either the Primary Server or Backup Server at any given time. In order for other servers and clients to maintain a seamless connection to the PAS regardless of which server it is active on, a virtual server name is used for all communication with the PAS. This virtual server name is also mapped to a switchable IP address that can be active on whichever server the PAS is running on.
The switchable IP address is created and handled by LifeKeeper using the IP Recovery Kit. The virtual server name is configured manually by adding a virtual server name/switchable IP address mapping in DNS and/or in all of the servers’ and clients’ host files. See the IP Local Recovery topic for additional information on how this works.
Additionally, SAP configuration files must be modified so that the virtual server name is substituted for the physical server name. This is covered in detail in the Installation section where additional instructions are given for configuring SAP with LifeKeeper.