Tablet Accessory User Manual

Starting an Engine
Chapter 4 Managing Engines 109
Database Service
When a database service starts, it attempts to connect to the primary engine unit. If
the primary engine unit is not online, the database service continues waiting for it
indefinitely.
When the primary engine unit starts up, the database service opens a
communication channel to the engine’s database service router object and becomes
available for use. The database service first asks the router for the name of the
database along with the username and password to use for logging on (provided to
the engine unit in the engine unit configuration file). It then logs on to the given
database using the username and password provided.
When you start a database service, you specify a component name and a priority
for it. A priority is simply an integer (positive or negative), with a higher numeric
value signifying a higher priority. It is suggested that you decide on a sensible set
of priorities. A default priority of “1” is used if you do not specify a priority.
When a database service starts, it may (or may not) establish a communication
channel with a router, and it may (or may not) log on to the engine database
successfully. The database service, therefore, can assume the states shown in the
following table. If a database service detects a failure in the communication
channel to the primary engine unit, it logs off the database and reconnects to a new
primary unit when its router comes online.
New database services can be started at any time, and they automatically become
available to the primary engine unit when they connect.
INFORM_PARTNER Communicates to partner that state
has changed to online.
64
STARTUP_COMPLETE Completion of startup operations.
Engine unit now online.
65
Database service state Description
RouterChannel=OPEN/CLOSED Communication channel with the database
service router is open or closed.
DatabaseState=TRUE/FALSE Database logon is successful or unsuccessful.
Startup Phase Description Phase #