In the flowable source-code you find some samples of migration documents:
For instance if you would like to upgrade an existing process instance to the latest process definition you can call the REST api as follows:
POST /runtime/process-instances/{processInstanceId}/migrate
{
"toProcessDefinitionId": "<lastProcessDefinitionId>",
}
or
POST /runtime/process-instances/{processInstanceId}/migrate
{
"toProcessDefinitionKey": "<processDefinitionKey>",
}
if you pass the process definition key only, it will always take the latest process definition. (requires v7)
Regards,
Simon