A process instance is generated when a business process initially receives a request. To generate process instances, when you define a business process in the development environment, set the instance generation to yes in the Receive Activity dialog box that defines the receive activity that initially receives a request.

For a business process for which process instances are to be generated, a process instance is generated each time the business process receives a request. Therefore, even when multiple requests are executed simultaneously, processes are executed independently for each request. The following figure shows the mechanism of process instances in a business process.

Figure 3-13 Mechanism of process instances in a business process

For details about the Receive Activity dialog box, see 1.4.7 Receive Activity dialog box in the Service Platform Reference Guide.

The following table describes the attribute information of process instances.

Table 3-2 Attribute information of process instances

Attribute	Description
Identifier	Identifier for identifying individual process instances. The identifier is unique within the same business process definition. (The version might be different in some cases.)
Business process definition name	Definition name of the business process to which the target process instance belongs. This attribute corresponds to the service name used during invocation from the service requester.
Business process definition version	Definition version of the business process to which the target process instance belongs.
Status	Status of the target process instance
Start time	Start time (GMT) of the target process instance Note: The time when the process instance transits to ACTIVE status
End time	End time (GMT) of the target process instance Note: The time when the process instance transits to COMPLETED status

The following figure shows the status transition of a process instance.

Figure 3-14 Status transition of a process instance

1. When you try to execute a process instance
2. When you try to execute an activity belonging to the process instance
3. When the global scope belonging to the process instance has been completed and the process instance terminates normally
4. When a fault occurs during execution of the process, and the process instance terminates in a fault because the fault could not be caught even in the global scope
5. When an exception occurs in the invoke service activity or scope activity, and the process instance is interrupted with an error
6. When you re-execute a process instance in which an error has occurred
7. When you re-execute a process instance that is already running

The following table describes the status of a process instance shown in Figure 3-14 Status transition of a process instance.

Table 3-3 Attribute information of process instances

Status		Description
ACTIVE status	Executing	The process instance is being executed.
ERROR status	Error	An exception occurred in the invoke service activity or scope activity, and the process instance is interrupted with an error.
COMPLETED status	Completed	The process's global scope has been completed (process instance is in the status of completed).
	Faulted	A fault occurred, and the process instance terminates in a fault because the fault could not be caught even in the global scope.