The IBCDASDI program initializes virtual
disks whenever the CYLBO=nnn operand of the DADEF control statement is specified. The CYLBO=nnn operand specifies the number of
cylinders to be initialized for a virtual 4 IBM VM/370 Service Routines Program Logic
disk. For information cn running the IECIAStI program and for a description of
the necessary control cards see the

Method of Operation
This section describes the execution of the
virtual disk initialization (IBCDASDI) Frogram and shows the processing associated
with: • Initializing virtual disks • Assigning alternate tracks.
Figure 1-2 shows the relationship of the
diagrams.
Diagram 1-2 Initializing a Virtual Disk
Diagram 1-' Overview of Virtual Disk Initialization 1-1 describes the OI the virtual
initialization program.
tiagram 1-2 shows
initialized.
hew tracks
majer
disk
are
Diagram 1-3 shows how alternate tracks
are assigned.
Diagram 1-3
Assigning Alternate Tracks
Figure 1-1. Key to Virtual Disk Initialization Method of Operation Diagrams Chapter 1. IBCD1SDI--The Virtual Disk Initializaticn program 5