Sun Microsystems iPlanet Integration Server 3.0, Process System Manual

Page: 29 / 368

What Is an iIS Process Engine?
Chapter 1 Introduction: iIS Process Management 29
Multiple Engine Systems
An iIS system does not need to be limited to a single engine. It can have any
number of engines. For example, one engine might be used for testing and another
used for production. (see
“Production Engines Versus Development Engines” on
page 83 .)
In other cases, organizational considerations or heavy load conditions might
require multiple production engines. While engines can communicate with one
another—a processes definition that executes on one engine can be invoked as a
subprocess by a process definition executing on another—each engine operates
independently. A single instance of a process definition executes on only one
engine.
In most cases, different process definitions would be executed on different engines.
For example, one process might execute on one engine while a subprocess it
invokes might execute on another. If the same process definition is executed on
more than one engine (to handle the workload of a large number of client users)
then client users would normally be divided up between the engines, each user
logging in to only one of the engines.
Multiple engines can run in a single iPlanet UDS environment, or can be spread
across a number of connected iPlanet UDS environments. However, there is no
mechanism by which one engine can fail over to another. iIS uses a different
mechanism to handle engine failover (see
“Failover Configuration” on page 33 ).