Sun Microsystems 3 manual 2Minimal Engine Configuration

iIS Process Engine Components

Figure 1-2Minimal Engine Configuration

Client Applications

Primary	iIS Process Engine
Engine
Unit
	Database
	Service

Engine

Database

Engine Unit The engine unit is an application that performs all the basic iIS engine functions (see “What Does an iIS Process Engine Do?” on page 36). The engine unit is a single iPlanet UDS server partition containing a number of manager objects (see Figure 1-5 on page 37). The engine unit, in performing its work, tracks the state of each process, activity, timer, process attribute lock, and session that it creates in the course of process execution. In a typical production situation, the engine unit maintains state information on tens of thousands to millions of objects. It is critical that this state information be kept in a persistent form should the engine unit fail and need to be recovered. For this reason, the engine unit writes all current state information to the engine database (described below).

Database Service The database service is an application that manages the engine unit’s database access. The database service is a single iPlanet UDS server partition that maintains communication channels with the engine unit, opens a session with the engine database, and writes and retrieves state information as required by the engine unit. The database service is a single–threaded application, and can handle only one request to the database at a time. (To see how to overcome this limitation, see “Full Configuration: Failover and Load Balancing Combined” on page 35.)

Engine Database The engine database provides persistent storage for state information maintained by the engine. It also stores registration information regarding all process definitions, assignment rule libraries, user profiles, and validations that can be executed by the engine. In addition, the engine database can be used to log historical information for tracking process execution over time. The

32 iPlanet Integration Server • Process System Guide • August 2001