Initial Program Load

When the system enters the wait state, the operator must specify the device to be used for SYSLOG (by pressing END/ENTER), and type in the name of the supervisor to be loaded, together with other information. The format of this information is described in The Supervisor Parameters Command.

The IPL program reads the supervisor into low storage. If a read error occurs while the supervisor is being read, the system goes into a wait state and an error code is set in the first word of processor storage. The IPL procedure must then be restarted.

After successfully reading in the supervisor, the system enters the wait state a second time. The operator then causes an interrupt which, in turn, causes IPL to read its commands from the IPL communication device.

The IPL procedure can be automated almost completely by making use of the Automated System Initialization (ASI) facility. This facility allows all control statements and commands needed for the complete operating system startup to be read from a sublibrary. For guidance on how to code and catalog an ASI procedure, refer to Understanding and Using z/VSE System Functions. For information on how to execute an ASI procedure, refer to Operating.

The following section describes the Supervisor Parameters command, followed by the IPL commands in alphabetical order: ADD and DEL must precede any other IPL command, except the SET and SYS commands. DLF (if specified) must be the first command after ADD and DEL. SVA must be the last IPL command.