Work with Events

Event activities of your process determines the start, end, and sometimes intermediate flow and behavior of your business process.

None Start Event

The none start event is used when no instance trigger is specifically defined. The none start event can be used as a placeholder when the required start event of a process is unknown, not yet defined, or implemented later by process developers.

None Start event None start events specify the beginning of a process where the process instance is created by another event or activity. The none start event doesn’t trigger a new process instance.

Similar to other start events, the none start event can’t have incoming sequence flows. It can only have default out-going sequence flows.


None start events are always used to define the beginning of reusable processes and subprocesses.

Form Start Event

The form start event triggers a process instance when a user submits a form. The form is specified in the implementation for the form start event.

Form Start event icon (a single circle with a form and pen in middle) The form is designed to get input from the user and present information relevant to the workflow. As you build the form, a business object is created to store the form data.

Message Start Event

The message start event triggers a process instance when a message is received. This message can be sent from another business process or from a service.

Message Start icon (a single circle with envelope in middle) Messages are types of data used to exchange information between processes. Just as data objects are used to define the data used within an application, messages are used to define the data used between processes or between a process and a service.

Similar to other start events, the message start event can’t have incoming sequence flows. Message start events require a default outgoing sequence flow.

You can expose a business process as a service that allows other processes and applications to invoke the process. To expose a process as a service, your process must begin with a message start event. Additionally, you must define the input arguments to the process, which are the data objects passed to the message start event.

The message start event allows you to specify input arguments to a process. These arguments define the message that other processes or services must send to the process during invocation.


Any process configured with a message start event will not appear in Workspace.

You can start a process configured with message start event using REST APIs.

  • Run /process-interfaces API to get the processDefinitionId.
  • Run /instances API with appropriate arguments to invoke a process.

See Create a Process Instance under REST API for Oracle Cloud Infrastructure Process Automation.

Timer Catch Event

Timer catch events lets you control the flow of your business process using a time condition.

Timer Catch icon

Possible uses of the time catch event include:

  • Creating a delay before running an activity

  • Configuring a deadline for an activity

  • Configuring a deadline for a process

  • Triggering additional activities after an elapsed time

You can use timer events as boundary events on an activity. Timer events can be defined as either interrupting or non-interrupting boundary events.

When an interrupting timer event fires, the token leaves the main process flow to follow the process flow the timer event defines. The process flow that an interrupting timer event defines can return directly to the main process flow.

When a non interrupting event fires, a copy of the token is created and passes through the process flow the timer event defines. The process flow that a non-interrupting event defines can’t return to the main process flow.

End Event

The end event marks the end of a process path. When a token reaches a none end event, it’s consumed. If there are no other tokens within the process instance, then the instance is complete.

End event icon (a single circle) Use the end event:

  • When your process isn’t required to perform any action after it completes

  • As a placeholder to be changed later during implementation by a process developer

For example, in a Sales Quote business process, the Sales Quote service task saves information about the sales quote to a database. Because no other work can be performed when the token reaches the end of a process, a none end event is used. After all process tokens reach the none end event, the process instance completes.

Description of none-end-example.png follows
Description of the illustration none-end-example.png

A process should have at least one end event. However there can be multiple end events based on how the process is designed.

Error End Event

The error end event lets you throw an error that can be caught by an error event subprocess activity or an error boundary event.

Error End Event
Use the error end event:

  • When the end of a process is the result of an error condition

  • To trigger an exception subprocess or a set of activities to handle a specific error.

You typically use the error end event with the error boundary event. The error boundary event is used to change the process flow based on a specific error. This flow usually ends with an error end event. See Error Boundary Event.

Terminate End Event

The terminate end event stops all parallel executions of a Process Automation instance.

A Process Automation instance can generate multiple parallel tokens by using parallel gateways and non-interrupting timer events. If you use the terminate end event at a process level, then it results in the termination of all parallel token, and the Process Automation instance changes to a completed state. If you use the terminate end event at a subprocess level, then it results in the end of all parallel executions in the subprocess, and the control returns to the next activity in the parent flow.

Terminate End Event
Use the terminate end event:

  • To handle a condition inside a parallel gateway that results in the termination of all tokens.

  • To handle a condition after a non-interrupting timer event that results in the termination of all tokens.

  • To terminate a concurrent flow that is not required.

The terminate end event immediately stops all work on a process and does not trigger error handling or other cleanup operations of the running process.

Error Boundary Event

Error boundary events are intermediate events that you can use to handle an error that occurs within a process flow.

Error Boundary Event
Use the error boundary event in the following activities that can throw service invocation failure exceptions:

  • A service task activity.

  • A subprocess activity.

The error boundary event catches an error that can occur during the execution of an activity and interrupts the execution of the process flow, and reroutes the flow out of an activity.