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.