UML22 — Section: 12.3.41 Streaming parameters for actions

Semantics, 2nd paragraph about streaming: "Streaming parameters give an action access to tokens passed from its invoker while the action is executing. Values for streaming parameters may arrive anytime during the execution of the action, not just at the beginning." Since an action represents a single step and is atomic. I think it is not possible that an atomic action comsumes further parameters during execution.

The stated issue presumes that action execution is atomic, which is not necessarily the case, and is certainly not the case for a call action to a behavior with streaming parameters. The whole point of streaming parameters is the semantics given in the quoted sentence, and they would be useless if this was not possible.
However, the quoted sentence is poorly worded, since it is behaviors that have parameters and are invoked, not actions. This may be causing the confusion and should be corrected.