Input CP •••••• ,'",,' moch'oe 0 console
Control
Cards
Notes Module
1 The general registers are cleared and IBCDASDI the PSWs are initialized. The SEREP flags in the machine check old PSW are
set to X'FF' and the program enters
a wait state with X'FFFF' in the
address field of the PSW. An attention interrupt identifies the
virtual machine console and the input
statement is read. The control cards
may be read from a 1402, 1442, 2400, 2501, 2520, 2540, 3410, 3420, or 3505 input device.
2 Next, the CLRSCAN routine links IBCDASDI to the control statements scan routine
at RDCARD. RDCARD returns a
pointer to a field and the length of
the field in registers SCANADR and
LENGTH, respectively, and an indica-
tion of the field type in location SWITCHRD. SWITCHRD is a one-
byte switch with the following settings: Meaning
X'50' Control statement error
X'40' Bypass
X'10' First control statement
has been read
x'oa' Operator found
X'04' Keyword found
X'02' Parameter found
Processing Output IPL the device containing
the IBCDASDI module.
2 Analyze the control cards.
3 If specified, initialize
the disk. (See Diagram 1-2 for details.)
4 If specified, get an
alternate track. I}8 I Initialized virtual disk with (See Diagram 1-3 for
details.) I .... CP Label Ref Notes
START 3 The initialization routine is entered
at VOLCHK if the volume label is to
be checked and at GEN5E if the
volume label is not to be checked.
Initialization starts with the I NT AL T
routine. CKINPUl 4 Control is passed to the GETAL TYZ routine if an alternate track is to be
assigned. If volume label checking is
requested, the CKVOLLBL routine
does the checking. Assignment of alternate tracks starts with the
GETALTX routine. CLRSCAN alternate tracks assigned.
Module Label IBCDASDI VOLCHK
GEN5E IBCDASDI GETALTYZ Diagram 1-1. Overview of Virtual Disk Initialization
6 IBM VM/370 Service Routines Proqra. Logic
Ref
Input Processing Output I I I I Initialize tracks.
2 Format and write track O. I :> 3 If requested, write the IPL program.
4 Format and write the
standard Volume Table of Initialized Virtual Disk Contents. Notes Module Label Ref Notes Module Label Ref 1 When the defective flag test is IBCDASDI INTALT 3 The user-supplied IPL initialization IBCDASDI WRTIPL suppressed, the home address is program is written. The program is
written followed by a maximum written on cylinder 0 track 0 or 1, or, length record 0 consisting of if the track is defective, on its
hexadecimal 55. The track is read assigned alternate.
and checked. A maximum·length I record 0 is written again, this time I I I consisting of hexadecimal 00. The I track is again read and checked. If a
data check is encountered, this I write sequence is repeated ten times. I 4 The DSCBs needed for the VTOe l,seDASDI r- ... IIT\/Tn,... rIVIIVIV,,", I are constructed: the DSCB (format 4)
and the DADSM DSCB (format 5). For the 3330 series, the alternate
track field in the format 4 DSCB is set to zero since no alternate If data errors still occur, the track is track cylinder is provided. Then, the
flagged as defective. An alternate VTOC is written at the user-specified WRTVTOC track is assigned when the device is location and normal end of job is
disk. For drum devices, a message is initiated. Control returns to CPo issued indicating the address of the
defective track. IBC10l1 BAD TRACK cccehhhh If the home address-record 0 area is
defective on a 2314 or 2319 disk
storage volume, an attempt is made
to move the home address-record 0 fields down the track approximately 800 bytes.
2 Track 0 is written. It consists IBCDASDI CONSTR2 I ;of two IPL records (or a dummy !PL record), a standard volume label and
up to seven additional labels. l Diagram 1-2. Initializing a Virtual Disk
Chapter 1. IBCDASDI--The Virtual Disk Initializaticn Program
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