IPL NQtg: You cannot load a shared system or one that uses disGontiguous saved segments into a virtual machine running in
the V=R area. An attempt to do so results in an error
message. PARM {p1 p2 ••• 1 passes up to 64 bytes of data (excluding the first blank
character after the keyword, PARM, but including all other
embedded blanks) to your virtual machine's general registers (4 bytes per register), starting with the high order byte of
general register o. since the registers are not cleared
before use, the PARM value should be some multiple of 4 bytes
to avoid having extraneous characters present in the low order
positions of the register. For example, you could key in PARr; eMSj) where represents a blank to ensure that the loy. ornAr positions of register 0 contain a hexadecimal 40. Whenever is specified, the remaining characters in the command
line are treated as parameters to be passed to your virtual
machine; therefore, PARK must be the last operand entered on
the command line.
1. IPL simulates the LOAD button and the device address switches on
the real computer console. The specified virtual address is
accessed and the required input/output operations are performed to
retrieve the IPL data.
2. the IPL procedure can be stopped just before loading
the virtual PSW except when initial program loading a named system.
Also, parameters can be passed to the virtual machine's general
registers. When the simulated load function is complete, CP initiates execution of the virtual machine by loading the 1PL PSi which was stored during the simulation process.
3. Care must be used when passing parameters to a named system (systemname). Named systems expect certain registers to be
initialized when they are given control. Indiscriminate use of the operand could overlay a previously initialized register
causing unpredictable results. 4. The IPL simulator program occupies one page (4096 bytes) of storage in your virtual machine. Therefore, if the system being loaded
utilizes data remaining in storage by the previous system, care
should be taken as to where that data is located. The starting
address of the overlaid virtual storage is: 256K and above
Less than 256K
For example:
= 1/2 the storage size
storage size=200K then the IPL Simulator is loaded at 100K. Section 5. Format of CP Commands 89

IPL 5. Any logical lines following the 1PL command are ignored since the execution of the IPL command transfers control from the CP environment to the virtual machine environment.
6. Some CMS routines and programs are stored on disks and loaded into storage as needed. Since this storage area is not contiguous with your virtual storage, the saved segments that are loaded in this area are called discontiguous segments (DCSS). However, the only saved segment a CMS user can replace is the CftSSE3 seqment. The user can indicate an alternate segment to be loaded bV issuinq an IPL command with this format: IPL {CUU .} PARM SEG=segmentname
systemname
SEG=segmentname
indicates the name of the saved segment to be loaded whenever
the CMS Editor, EXEC processor, or as simulation routines are
needed. Eiqht characters must be entered for segmentname;
either assiqn an 8-character segment name when you code the macro for your installation, or be sure that the
operator enters trailing blanks if segment name is less than eight characters long.
The CMS batch facility loads whatever segment is specified
on the first IPL command issued for the batch virtual machine. Thus, if the first 1PL command for a CKS batch facility machine is: 1Pt CMS PARM SEG=CMSSEG02 all subsequent IPL commands issuej by the CftS batch facility specify the same segment name (CMSSEG02). 7. The option in the PARM operand indicates that the :ftS initial proqram load is beinq performed in a batch instead of an int.eractive virtual machine. This option causes the :KS nucleus to issue the CMSBATCH command to load the batch processor. Specifying
the option eliminates the need for operator intervention
between jobs. Consult VM/370 gng for
information on the CMSBATCH facility.
8. CMS users can use the PARM operand to pass the AUTO:R (automatic
carriage return) option to the CMS initialization routine. AUTOCR simulates the pressing of the ENTER key as input to the virtual
machine. This results in automatic execution of the user's PROFILE EXEC, if it exists on virtual minidisk 191.
Note: For a disconnected CMS service virtual machine, this mechanism can prove to be very useful. The name of a :MS restart may be specified in the CMS nucleus. In the event of an
ABEND, the specified restart routine receives control instead of
the service virtual machine entering a disabled wait state. If
this routine issues an 1PL eMS PARM AUTOCR command, the PROFILE EXEC executes initial setup procedures that allow the service virtual machine to reestablish itself.
After a successful 1Pt, any responses you receive are those from the operating system that was loaded and initialized. 90 VM/370 CP Reference for General Users