See (p3,womb) for current methods.

The kernel is started for the first time by IPL'ing a 370. This is called "IDL" for "initial domain load". {This is in contrast to subsequent kernel IPL's for restarting from checkpoints.}

At the conclusion of an IDL there are a few nodes and pages. There is a domain formed from these nodes called the initial domain. This domain has the only process. An initial program supplied by whoever controls the machine is in the memory tree of the initial domain and this domain holds the initial keys.

Thus the initial program is ultimately responsible for the machine utilization policy.

Note that the code that is present at the conclusion of IDL must be sufficient to communicate with the outside world. Currently this means Tymnet or mag tape.