Page of GC20-1801-10 As Updated April 1, 1981 by TNL GN25-0837
Directory
Creating Your VM/370 Directory
The VM/370 directory contains the entries of all potential virtual
machines that are permitted to logon the VM/370 system. Without the
proper directory entry, a user cannot log on to VM/370. The entries in
the directory contain the user identification and password, the virtual
machine I/O configuration, associated virtual and real addresses, disk
usage values, virtual processor storage size, and other options. These
options are discussed in the directory program control statement
descr ipt ions.
Each user in the directory, except those whose password is NOLOG, must have at least one device. Any of the various devices described meet
this requirement; for example, the device may be a console or a spool
device. The number of virtual devices for a virtual machine cannot
exceed the value determined by (7FFF/VDEVSIZE), where VDEVSIZE is the
size of the VDEVBLOK. If a greater number of virtual devices is
specified, results may be undesirable.
The VM/370 directory usually resides on the VM/370 system residence
disk, and is pointed to by the VOL1 label (cylinder 0, track 0, record
3). The VM/370 Directory program (module DMKDIR, invoked by the DIRECT
command, or run standalone) processes the control statements you prepare
and writes the VM/370 directory on disk. You already described your
installation's real configuration when you created the real I/O configuration file. NOw, you describe the many virtual configurations
for your installation with the Directory program control statements.
To create a VM/370 directory, you must: • Prepare the Directory program control statements • Format and allocate the DASD space to contain the VM/370 directory • Execute the Directory program At this time, you should prepare the Directory program control
statements. Later, during the system generation procedure, you must (1)
format and allocate DASD space for the VM/370 directory and (2) generate
it. The step-by-step description of the system generation procedure that
is in Part 3 of this manual reminds you to create your VM/370 directory.
Considerations for Preparing the Directory Control
Statements
First, prepare a directory control statement that defines the device on
which the VM/370 directory is to be written. This statement (DIRECTORY) must be the first control statement in the input to the Directory
program, and is followed by the sets of statements describing your
installation's virtual machines.
Next, prepare Directory proqram control statements describing each
virtual machine in your installation. The descriptions contain
accountinq data, options, and virtual machine configurations for each
virtual machine that appears in the VM/370 directory. Information about
coding these control statements is found in the section, "The Directory
Proqram. " VM/370 does not check for overlapping extents; therefore, you must
ensure that minidisk extents defined in the VM/370 directory do not
overlap each other and (in the case of 3330, 3340, and 3350 disks) do
not overlap the "alternate track" cylinders. If overlap conditions
exist, file data damage is inevitable. Part 2. Defining Your VM/370 System 183

or As Updated April 1, 1981 by TNL GN25-0837
Directory You must define one or more virtual machines for the operator and
should define virtual machines for the system analyst or system
programmer.
The operator's virtual machines should be able to control: • The VM/370 sessions • Allocation of machine resources • Spooling activity • Online disk areas You should also define virtual machines for system analysts that are
equipped to: • perform system analysis • Modify certain VM/370 functions
and additional virtual machines to update or operate: • The CP system I 11 C 1-1.3 ::> y L e In • The RSCS system, if you generate one • The hardware • other operating systems that run in the virtual machine environment • The Installation Verification Procedure SYSTEM SUPPORT VIRTUAL MACHINES At system generation time, two' additional virtual machines should be
created beyond those needed by normal users (one each for hardware and
software support). The IBM FE programming support representative should
be consulted when the configurations for these virtual machines are
being determined.
The hardware support is for: • The processor, which must be supported in a dedicated environment
because there is no method currently available that allows concurrent
support of the processor, real storage, or channels when executing
problem programs. • The input/output equipment, which can be supported using online test (OLT) under OLTSEP. The OLTSEP program can be executed in its own
virtual machine.
Any of the offline testing capabilities of the system devices can be
used on inactive units while the system is operating.
To perform online hardware support, a virtual machine must be defined
in the VM/370 directory for the IBM service representative. The virtual
machine should have enough virtual storage defined to execute OLTSEP. Normally, the service representative requires that the device being
tested be dedicated to his virtual machine. (The system operator can
dedicate devices to a virtual machine by issuing the ATTACH command.)
Also the virtual machine for hardware support should have the minimum
configuration required to run online tests, and provide access to CKS with a read/write minidisk. Privilege class F should be assigned to
allow the hardware diagnostics to be run, and error recording and
retrieval facilities to be utilized.
184 IBM VM/370 Planning and System Generation Guide