Clusters (multiple-node
systems) — Concepts and terms
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Use of multiple nodes can provide high system availability and a degree of fault-tolerance, as the failure or offline status of one node does not affect the ability of users connected to another node to continue working.
When a server node is running, the server appears as an instance of the Data-Admin-Nodes class.
You do not need to define instances of this class. The system creates an instance each time that Process Commander starts on that server. (You can start and stop the engine software on each node independent of the state of other nodes.)
All the nodes share a single common PegaRULES database. The PegaRULES engine software on each node must be a compatible version — preferably an identical version — of Process Commander. OLSOK
Each node contains an in-memory cache of recently accessed rules that may, in multiple-node operations, contain different instances. (The correct and most recent versions of the rules are always in the database.) Periodic pulse processing synchronizes the contents of the rule cache on a node to the latest copy in the PegaRULES database. Optionally, you can associate a description of each node using Data-Admin-Node instances. The information you enter appears on the System Nodes Detail display.
Node names are limited to 32 characters.
Q-1943
In a multinode Process Commander system, ensure
that the clocks of every node are synchronized, and the clock on
the server hosting the PegaRULES database is synchronized. Most vendor
operating systems offer a means to accomplish this. Many calculations and
decisions such as time-qualified rules, service level rules, and
management reporting depend on clock settings and intervals. See the Pega
Developer Network article 
PRKB-10206 How to synchronize
server clocks and database clocks with NTP for correct service level
computations ion for more information.
UNIX and Linux-based systems require special
configuration settings to ensure that the JVM recognizes Daylight Savings
time. If not set, the times recorded in the Process Commander log may not
match the server clock time. See IBM Tech Note "Incorrect time
stamps displayed by an application or in log files" about the TZ
environment variable, and additional details for IBM WebSphere.
These Pega Developer Network articles are relevant:
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AES, cluster, load-balancing, horizontal cluster, node, node ID, pulse, system ID, time-qualified rules, vertical cluster |
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About the
System data instance
About System Node data instances |