Each step in the process block has a nUlbered key (1, 2, 3, ••• ) and each
substep has an alphabetic key (1, B,
C, ••• ). The related cOllent in the Notes
section has the same key. The key that
relates the Frocessing step to a note is
inside a box, and the key that relates a
processing substep to a note is indented so
that it is easily visible. Illustration Numbering
Figures and
numbered. The system is:
diagrams format Figure x-nn
D iagrall X- nn
are
of the
separately
numbering
2 IBM VM/370 Service Routines Program Logic
where X designates the chapter (one through
ten) and nn designates the relative
position of the figure or diagral within
the chapter. For exalple, Figure 2-3
is the third figure in Chapter 2. Diagral 3-1
is the first lIethod of operation diagral in
Chapter 3.
This publication is intended to acquaint
the systel prograller, and those
programmers responsible for updating VM/310 service routines, with the operation of
these service routines.

Chapter 1. I BCDASDI-The Virtual Disk Initialization Program
Introduction
The IBCDASDI program initializes virtual
disks. A virtual disk- is a logical
division of a physical DASD that is used by OS and DOS for user direct access storage
space with VM/370. Por virtual disk initialization, the
following functions are performed:
1.
2.
3 ..
4.
5.
6.
Alternate tracks are assigned
those previously designated
defective.
for
as
A home address and track descriptor
record are written. IPL records are written on track 0 of
the virtual disk.
A voluae label is written on track 0 of the virtual disk.
A volume table of contents (VTOC) is
constructed and written on the virtual
disk.
An IPL program is written on track 0 of the virtual disk (if requested).
1. Surface analysis of each track is
performed (if requested.; Alternate tracks are automatically assigned, if
necessary. Por alternate track assignment, the
following functions are performed: 1.
2.
The first available operative
alternate track is selected from those
indicated in the VTOC. The address (CCHHR) of the priaary track is written in the count field of
the selected alternate track. The
address (CCHHR) of the alternate track
is written in the count field of the
primary track.
3. The VTOC DSCB is modified to reflect
the new status of available tracks. !£te: The IBCDASDI program does not assign
alternate tracks or perform surface
analysis for 3330 or 3350 disks. INVOKING THE VIRTUAL DISK INITIILIZATICN PRCGRIM The IEC!ASDI program may be loaded as a
card deck, or as card images on taFe. Control statements for the program can
follow the last card (or last card image)
for the program, or can be entered via a
separate input device.
To execute the IBCDASDI Ircgram: 1. Put a copy of the IECDISDI object deck
into your virtual card reader, or
mount and attach the tape containing
the object program.
2. Load the object program from the
virtual reader on tape by issuing the CP IPt co.mand for the appropriate
virtual device address. When the
program is loaded, an ebabled wait
state is entered with the address
field of the PSi containing the
hexadecimal value FFFP. 3. When the program is leaded and waiting
for input, signal attention from the
virtual console device. The message DEPINE INPUT DEVICE is sent to the virtual console. Enter
the following resFonse from the
virtual console: INPUT=type cuu type is the virtual device type of
cuu
the device containing
control statements.
device types are 1402, 2400, 2501, 2520, 2540, 3420, and 3505. the Valid 1442, 3410, is the virtual device address ef
the device containing the
control statelents. Control statements are printed on the message output device. It the end of job,
the END OF JOB message is printed en the message output device and the program
enters the wait state. Chapter 1. IBCDASDI--The Virtual Disk Initializatien Program 3