Reconfiguring an Engine
116 iPlanet Integration Server • Process System Guide • August 200 1
How to Tune Process Execution
The performance of an engine depends on available system resources, such as
memory. For example, if engine memory resources become overtaxed, engine
performance can degrade, and an engine can even fail.
It is hard to know in advance the memory resources required under production
loads. Memory requirements depend upon the number of sessions being
supported and the number and complexity of concurrently executing process
instances—the number of activities, timers, process attributes, and so forth. Hence,
to prevent failure, it is necessary to monitor the performance of the engine under
production loads, and to reconfigure it when performance begins to degrade.
A number of configuration options are availabl e for tuning process execution, as
described in Step13 on page 102:
•Maximum Number of Sessions
•Maximum Number of Processes
•Memory-resident Process Limit
•Swap-out Interval
For example, you can use the first two options to limit the number of concurrent
sessions or process instances that the engine supports. While this can keep process
execution within resource limits, it also limits the load that an engine can support.
A more sophisticated approach is to use the engine’s advanced process
management capabilities. These capabilities allow the engine to swap out dormant
process instances in order to reuse the memory space they occupy. When these
process instances are subsequently needed, they are swapped back into memory,
replacing other process instances that are not currently being used.
In other words, only the most recently needed process instances are kept resident
in memory. By swapping process instances out of and back into memory, the
engine can support process execution loads that would otherwise exceed available
memory resources and cause the engine to fail. Of course, there is overhead
involved in this kind of process execution management, so in some cases,
performance can be impacted.
The engine’s mechanism for managing process execution depends on the values of
two engine configuration options: the Memory-resident Process Limit and the
Swap-out Interval. As process execution proceeds, the engine checks that the
number of process instances resident in memory does not exceed the
Memory-resident Process Limit. If it does, the engine swaps out the least recently