The nativearray is set to readonly in the declaration and in the job. When the job is not running, I can access the nativearray from another thread without error messages. When the job is running, I get the message its forbidden. What's the sense here? The nativearray is completely readonly, so there can't be any thread safety issues. I need this for my setup as I have a background worker queue system which is doining non-frame critical work which really works well for me. EDIT: Title updated for more clarity. The question is about c# task threads accessing readonly nativearrays.