Tablet Accessory User Manual

Starting an Engine
106 iPlanet Integration Server • Process System Guide • August 2001
The governor has four internal states, depending on its connections with the engine
units:
As the governor changes state (that is, as engine units start up and shut down), it
determines which engine unit is primary based on the state of the engine units
before the change occurred. For example, in going from BOTH to E2, the governor
will make EngineUnit2 primary if that unit had been the backup before the state
change (a normal failover scenario). In going back, from E2 to BOTH, however, it
will retain EngineUnit2 as primary, even if that engine unit is marked as the
preferred backup. (You can override the Governor to return EngineUnit1 to
primary—see “Changing Engine States” on page 122.)
Engine Unit
When an engine unit starts, it attempts to connect to both the governor and its
partner engine. It waits for a timeout period and exits if no connection is
forthcoming. (If the engine configuration file specifies no engine unit partner, the
engine unit can start up standalone, without requiring a governor or partner.)
If an engine unit starts after the governor has started, the engine unit connects to
the governor. The governor determines if the engine unit is primary or backup,
depending on the engine’s preferred designation or whether the engine is the first
unit to start (in which case it becomes the primary unit). If the engine unit is
primary, it attempts to come online. If the engine unit is backup, it enters a standby
state in which it does not attempt to come online.
Governor state Description
IDLE Not connected to any engine units
E1 Connected only to the first engine unit to start up
(EngineUnit1)
BOTH Connected to both engine units
E2 Connected only to the second engine unit to start up
(EngineUnit2)