For the multiple application-instance scenario, each instance is assigned a unique DVIPA. The VIPADEFINE keyword of the VIPADYNAMIC configuration statement is used to create the DVIPA on the stack where the DVIPA is normally expected to be active. When the VIPADEFINE statement is processed in a TCP/IP profile, corresponding DEVICE, LINK, HOME, and BSDROUTINGPARMS statements are generated automatically for IPv4 addresses. For IPv6 addresses, an INTERFACE statement is automatically generated. Routing daemons are automatically informed.
Additional configuration is required on other stacks in the sysplex to indicate which stack should take over the DVIPA in the event of a failure. The VIPADYNAMIC statement has a VIPABACKUP keyword for this purpose. A VIPABACKUP configures the DVIPA but does not activate it until it is necessary. Because more than one TCP/IP can back up a single DVIPA, a rank parameter on the VIPABACKUP statement determines the order in which several stacks will assume responsibility for a DVIPA.
The stacks in the sysplex exchange information on all VIPADEFINEs and VIPABACKUPs defined in the sysplex, so that all are aware of which stack should take over a particular DVIPA. The list of backup stacks for a specific DVIPA can be different from the list of backup stacks for all other DVIPAs.
In the multiple application-instance scenario, instances of the application in question are activated among sysplex nodes according to some plan, presumably related to balancing workload across available capacity. This activation is done independently of VIPA takeover. Configure the associated DVIPAs as follows:
After these steps are complete, start the affected TCP/IPs (or modify their configuration using the VARY TCPIP,,OBEYFILE command), if applicable, configure DNS for the application names, and start the application instances. From that point on, the TCP/IPs in the sysplex will collaborate to ensure that each dynamic VIPA is kept active somewhere within the sysplex as long as there is at least one functioning TCP/IP which has been designated as backup for the dynamic VIPA.