From version 18.1 onwards, there is an important change in behavior of Automation Engine workflows. In case an output pin of a task or workflow control has no output file, a workflow can now continue with a so called ‘empty token’ where in previous versions, the workflow would have stopped.
The reason for this change is to avoid a workflow from stopping ('stranding') where it did not make sense to stop. Tasks that do not really need an input file, should not be blocked from starting if there is none.
This means that after an upgrade to 18.1, a workflow can now unexpectedly continue where it used to stop. Some workflows might have to be adapted after an upgrade.
The list of tasks and workflow controls that can now startupon receiving an empty token:
Wait for Action (Checkpoint)
Integrate with WebCenter
Interact with Web Service
Wait for Files
Interact with Database
Create XML File
All workflow controls (Router, Select Job...)
The following tasks can also now create an empty token on an output pin in the workflow, which can triggers another task or workflow control to start:
Interact With Database
Wait for Action
Some practical examples
A Select File task cannot find the requested file, causing the workflow to strand in version 18.0.x - even if it would make sense to create an XML file (no input file is needed to start this task).
With the same setup in version 18.1, the Create XML File task will be started by an empty token.
In the below example, the Interact with Database task is configured to do an insert statement (so, it will not produce any real output) and the Data Collector is configured NOT to group collected data (so all input tokens are kept as is).
In version 18.0.x, the Interact with Database task will not create an empty token and therefor won't start a task.
In version 18.1, the Interact with Databasewill create an empty token, which will trigger another start of the Map Data task.
Adapt the workflows to the new and more logical behavior.