DEFINING VIRTUAL DEVICES When using the SPOOL, DEDICATE, and SPECIAL control statements to define
virtual devices, specify virtual addresses that do not conflict or
ccntend with the virtual control unit interface. conflict or
contention occurs because devices can require special I/O interface
protocol frem control units, such as for shared and nonshared subchannel
operations. Putting devices that require different real control units
on the same virtual control unit can result in a hung or busy condition.
To avoid this problem, users must define (and separate) devices within
their own control unit range.
For example: If the directory entry specifies: SPOOL 102 3211 SPECIAL 103 3270 the control unit 0 on channel 1 controls both an unshared device (the
3211 printer) and a shared device (the 3270 display unit). processing
of channel prcgrams involving these two devices can result in a hung or
busy condition. AUTOLOG FACILITY AUTOLOG is a convenient way to initiate large production operating systems with many I/O devices that run under VM/370. The I/O devices
needed by these operating systems require considerable contiguous
storage space for the I/O control blocks established by Vft/370. When these large operating systems are started after other, smaller users
have been using V8/370, the contiguous storage space may not be
available. When there is insufficient contiguous space, the logon of the
virtual machine is successful; however, there may be an insufficient
number of I/O devices to run the operating system and its application
programs.
To ensure sufficient contiguous storage space, log on those virtual machines after loading V8/370. • Have the V8/370 system operator issue the CP AUTOLOG command before
enabling user terminals. • Define the AUTOLOG1 virtual machine in the VM/370 directory. The AUTOLOG1 userid can be used to logon and load virtual machines that
require substantial contiguous storage.
Before enabling user terminals, the V8/370 system operator can issue the CP AUTOLOG command for each production virtual machine that requires
substantial contiguous storage. The directory entry for the userid
indicated by the CP AUTOLOG command must contain an IPL statement for
the desired operating system. For more information about the CP AUTOLOG command, refer to the 46 IBM VM/370 operating Systems in a Virtual

After the VM/370 console operator loads the VM/370 system, VM/370 initiates one predefined operating system to run as a virtual machine
without oFerator intervention, provided these two conditions are met:
1. An AUTOLOG1 virtual machine is defined in the directory.
2. The AUTOLOG1 directory definition includes an IPL control statement
specifying an operating system. !2te: The AUTOLOG1 facility initiates a virtual machine with an oFerating system in disconnect mode. If that virtual machine issues a
READ command to its own unavailable console, VM/370 terminates the
virtual machine. WRITE commands to an unavailable operator's console
merely cause the loss of information that is not spooled; no
termination occurs.
To use AUTOLOGl to initiate several virtual machines, have the VM/370 directory statements load CMS for the AUTOLOG1 userid. The CMS PROFILE EXEC would contain several CP AUTOLOG commands. Each AUTOLOG command
initiates one virtual machine containing a production operating system. When using the CP AUTOLOG command, the directory entries referenced by
the CP AUTOLOG command must contain an IPL statement. When the Froduction virtual machine is loaded directly by an IFL statement in AUTOLOG1, an operating system user gains access to the
virtual machine by logging on as AUTOLOGl with the appropriate password. When the production virtual machine is loaded (as a result of a CP AUTOLOG command in the CMS PROFILE EXEC), an operating system user gains
access to the virtual machine by logging on with the userid specified in
the CP AUTOLOG command. When the user logs off, contiguous storage space is relinquished. If
the user wants to keep the virtual machine's I/O blocks in contiguous
storage and temporarily relinquish use of the virtual machine, the user
issues the CP DISCONN command. To reestablish usage, the user issues
the CP LOGON command to to the virtual machine.
The fcllowing example uses the AUTOLOG1 facility with an IPL statement. USER AUTOLOG1 PASSWORD 256K ACCOUNT ACCTNO BIN3 1PL 350 OPTION ACCT CONSOLE 01F 3215 SPOOL OOB 2501 SPOOL OOC 2540 R SPOOL OOD 2540 P SPOOL OOE 1403 MDISK 350 3330 101 30 OSDOS1 W MDISK 351 3330 1 20 UDISKl W Section 1. General Considerations 47