SAP Message WF012 - Process type is locked by another agent/session

Diagnosis
The process is locked by another user or another session of your own.
When the process definition is being edited, a process requiring thisdefinition cannot be executed.
Process type X can also not be changed while a process of type X isrunning.

System Response
The action cannot currently be carried out and was rejected.

Procedure
Please repeat the action later or inform the user &V1& who has lockedthe process.