# OnDemand

The **OnDemand** trigger is initiated through a direct REST API invocation, specifically the Job Manager Submit API. 🚀 See the [Job Manager APIs](/data-mover-1.21/api/job-manager-apis.md) page for more details.

For example, the OnDemand trigger can be used to invoke a contract action by a script or application external to Data Mover.

The API accepts variables, which are passed to the instance as process variables. Any variables specifically declared in the template when creating a contract are combined with the set of variables supplied through the REST call. If the same variable name appears in both the contract template and the REST request, the value from the REST request takes precedence. 

The execution of an OnDemand trigger does not add execution variables.

For the **OnDemand** trigger, Data Mover provides a set of **system workflow templates** that must be used in input, mediation, and output contracts. You can find the complete list on the following pages:

* [Workflow templates for input contracts → Trigger type: OnDemand](/data-mover-1.21/workflow-templates/system-workflow-templates/workflow-templates-for-input-contracts.md#trigger-type-on-demand)
* [Workflow templates for mediation contracts → Trigger type: OnDemand](/data-mover-1.21/workflow-templates/system-workflow-templates/workflow-templates-for-mediation-contracts.md#trigger-type-on-demand)
* [Workflow templates for output contracts → Trigger type: OnDemand](/data-mover-1.21/workflow-templates/system-workflow-templates/workflow-templates-for-output-contracts.md#trigger-type-on-demand)


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