What is the difference between context_param from the command-line and contexts defined within Talend that are populated by a file?
Does context_param overwrite or take precedence over a context loaded from within a Talend job (via a file context load)? Or vice-versa?
Does context_param 'create' a context (variable) or does one have to be defined within the Talend metadata prior to using context_param from the command-line?
The order the context variables are populated is (not absoluty sure between 2 and 3):
In any case, variables must be define in the jobs else they can't be used (compilation error).
So, they are never created "on demand", just populated.