Sun Microsystems iPlanet Integration Server 3.0, Руководство по системе управления

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Starting an Engine
Chapter 4 Managing Engines 107
If an engine unit starts before the governor, but after its partner has started, then it
must negotiate with its partner to establish which unit is to become primary. If one
unit has been marked as the preferred primary, then that unit becomes primary. If
neither unit has been marked as the preferred primary, then the negotiation
randomly determines which of the two becomes primary. If the governor starts up
in the middle of this negotiation, the governor takes over and decides the issue. If
the governor starts up after the negotiation is complete, the governor accepts the
negotiated decision.
When an engine unit starts, it goes through an internal, transitional state
(EMBRYONIC), then assumes one of two persistent states, ONLINE or STANDBY,
depending on whether it is designated as the primary or backup engine unit. The
STANDBY state is assumed immediately upon startup; however, the ONLINE
state is achieved only after the engine unit has passed through a number of startup
phases, such as logging on to the engine database and performing registrations
with the Name Service. The startup phases are described in more detail below.
As a system manager you can override the state of an engine unit after it has
started. For example, you can set the primary engine to a STANDBY state, and then
set its partner to an ONLINE state, making the partner the new primary engine
unit. The engine unit states are described below.
Engine unit state Description
EMBRYONIC Internal, transitional startup state.
ONLINE Normal state of the primary engine unit. It is running,
connected to the engine database, and can accept client
sessions.
STANDBY Normal state of the backup engine unit. It is running, but is
not connected to the engine database and cannot accept client
sessions.