Seems this should be obvious but what happens when you delete a journal entry? What does the system do?

Are you asking this as something has happened when you have deleted a journal? I presume the accounting entries are just removed and the transaction is deleted - like it was never created, except for the numbering would be 1 off. I know Netsuite does some recalculations in the back ground on some transactions (Not sure if it would on the journal though!)