Chapter 3. The Format Service Program Introduction The Format/Allocate service routine is a
standalone Frcgram which: • Formats all or part of a DASD device • Allocates DASD space • Creates volume labels
for IBM 2314, 2319, 3330, 3340, 3350 series, and 2305 series direct access
storage devices. Operands entered from the IPL device
and/or a 1052 console centrol the execution
of the Format program. FORMAT OPERATION The Format program writes 4096-byte (one
page) records on all the specified
cylinders. The records just written are
then read tc verify the disk surface. Any
records not Fassing the read-after-write
check are counted. When the format
operation is complete, a summary of the
addresses of the unusable pages is written
on the console.
The first three records of cylinder 0 contain special sYstem data includinq the volume label. If the format operation
includes cylinder 0 any existing volume label is read first and if an OS For.at 4
label is present, the information in the
label ccncerning alternate track
assignments is carried forward to the new
label. Then the new volume label is
written on the DASD device.
If cylinder 0 is not to be formatted,
label checking is performed.
If unrecoverable DASD errors occur
during the formatting operation, the format function is canceled, the message DMKFMT735E FATAL DISD I/O ERROR is issued, and the next control statement
is read. LAEEL-ONLY OPERITICN In a label-only operaticn, a new volume latel is written on cylinder 0, track 0, record 3 of the DISD device. No label checking is done tefore the new label is
written. The device must already be
formatted before a late 1 oFeration can be
performed. ALLOCATION OPERATION In an allocation operaticn, disk space is
assigned on the specified device in units
of one cylinder. This disk space may be
used as: • Temporary space (TE!P) • Permanent space (PER!) • Iirectory space (DRCT) • Temporary user space (TDSK)
The input parameters provide the
information needed to update the allocaticn
tatle. When the END allocation statement
is processed: • The allocation table is written in the
byte allocation map on cylinder 0, track 0, record 4 of the DISD device. • The results of the allocation cperation
are displayed at the console.
The IISD device must already be
formatted before an allocation operation
can be performed. EXECUTING THE FORMIT FROGRI! The sequence for program is:
executing the Format 1. Ready the DISD device.
2. Ready the reader. The reader .ust
contain the For.at/Illecate program
and .ay also contain control cards fer
the prograa. Chapter 3. The Format Service 63

3. IPL the reader.
4. If a console is not located at either
address 009 or 01F, signal attention
from the console so the Format program
can establish the address of the
console.
5.
6.
7.
The prcgram title is printed. When there are no control cards in the
reader, the program requests control
statements by sending prompting
messages to the console. When control cards are in the reader,
they are processed. The prompter
messages are displayed with the
response field updated from the
control sta tements already entered
64 IBM VM/370 Service Routines Program Logic
through the card reader. The program requests additional input, which can
be entered via the reader or console.
8. The program issues messages indicating
the start or end of an operation.
9. 10. An operation in progress aay be
canceled by signaling attention from the console. Execution resumes with
the next The Format/Allocate program cancels an
operation if a an unrecoverable DASt I/O error occurs. A message indicating the cause of the error is
displayed.