SPOOL allows you to start/stop the spooling of a virtual console and modify the options for virtual spooling
Reference the detailed IBM manaul page here.
Some of the more common uses are:
Setting the class of input accepted by your virtual reader. The "*" class when set on a reader will accept any
class input submitted to it.
Printer, Punch, and Reader spool files can be placed in a hold status when created (PRT & PUN) or after they are
read (RDR). They must then be released manually with the CHANGE command when appropriate.