The IBM-recommended implementation, if you are running
in a sysplex, is to set up your TCP/IP network with Sysplex Distributor.
This makes use of dynamic virtual IP addresses (DVIPAs), which increase
availability and aid in workload balancing.
The following are recommended environment considerations for Sysplex
Distributor:
- You need only basic sysplex functionality to utilize DVIPAs
and Sysplex Distributor because these functions do not rely on data
stored permanently in the coupling facility.
- Set up your system such that each HTTP request connection results
in no saved state or the HTTP and application servers are configured
to share a persistent state.
When doing this, HTTP server plug-ins send no-affinity connections
to Sysplex Distributor (a secondary connection load balancer) with
more information to make a better distribution decision.
Note:
As long as the HTTP catcher itself is not bound to any particular
IP address, the application-specific DVIPA can be used when affinities
dictate a particular server. This allows use of the Sysplex Distributor
server address for requests that are not tied to a server, covering
the same set of servers in the sysplex.
Since the client
connection terminates at the plug-in/proxy, and the secondary connection
is established by the plug-in itself, there is no need for network
address translation.
Requests to the node agent do not require any affinity, and each
request is independent of other requests. Sysplex Distributor can
be used to balance work requests among node agents, with the added
benefit that Sysplex Distributor knows which nodes are available.
Therefore, it will never route a work request to a node that is not
listening for new connection requests.
Note: If you
are running z/OS® Version 1.2 or earlier, Sysplex Distributor
is limited to distribution on only four ports for a particular distributed
DVIPA. You may configure multiple DVIPAs when more than four ports
exist, but this is a configuration burden.