Page of GC20-1806-9 As Updated April 1, 1981 by TNL GN25-0834 Note that before the ALLOCATE function was invoked, cylinder 0 was
formatted and labeled CPDSK2. The area associated with the first three 4096-byte blocks on cylinder 0 are not used for spooling but contain
system information (page allocation map, label, and so on).
These CP-formatted volumes can be made usable by CP in one of two
ways: 1. They may be attached to the system by the VM/370 operator.
2. Their volume serial numbers may appear in the SYSOWN macro in the DKKSYS module. The CP system residence volume's serial number must
appear in the SYSOWN macro. IBCDASDI--Generallnformation VM/370 uses the OS utility program IBCDASDI for disk initialization, for
disk formatting, and for assigning an alternate track. The execution of IBCDASDI is performed from the virtual card reader and the technique is
descr ibed in "Invoking IBCDASDI" later in this section. - Corresponds roughly to what is referred to as
"initialization with surface analysis" or "non-quick DASDI". It is
invoked by a DADEF statement when its PASSES operand is specified or
defaulted as a value greater than 0 (and for 2314, 2319, and 2305 the FLAGTEST=NO operand must also be specified). Each track is tested and
alternate tracks will be assigned to tracks that prove defective.
Pre-existing flags and alternate assignments are ignored. Record zero
is rewritten on all tracks. For some device types, home addresses are
also rewritten on all tracks. Disk initialization can be performed on 2305, 3330, 3340, and 3350 real (dedicated) disks and on 2314 and 2319
minidisks as well as real disks. Initialization will generally be
required when a disk (or a 2314 or 2319 minidisk) is in an initial or
unknown state. Note: whenever disk initialization is done, disk
formatting is also done. JQte: Disk formatting will not reset (clear) the count field. DISK FORMATTING Corresponds roughly to what is referred to as "initialization without surface analysis" or "quick DASDI". It is
invoked by a DADEF statement with PASSES=O,BYPASS=YES specified.
Formatting consists of writing IPL records 1 and 2 standard OS volume
labels on track 0 cylinder 0 and of writing an OS volume table of
contents (VTOC). Since a disk's as Format 4 label always contains a
record of how many alternate tracks remain available for assignment,
this information must be computed before the Format 4 label can be
written. To compute this, IBCDASDI reads the "alternate tracks"
cylinders. Disk formatting can be performed on any device, real or
minidisk. Disk formatting will generally be required when standaru
labels must be created. ASSIGNING AN ALTERNATE TRACK -Invoked with a GETALT statement. This is
an explicit- analternate to be assigned to the particular
track that is specified. (Note that disk initialization may also assign
alternate tracks.) Only the specified track is affected, so label and VTOC data is generally preserved. Alternate track assignment can be
performed on 3330, 3340, and 3350 real (dedicated) disks and on 2314 and 180 VM/370 Operator's Guide
2319 minidisks as well as real disks.
l The last cylinder in any 2314 or
2319 minidisk initialized by IBCDASDI is reserved and used as the
"alternate tracks" cylinder. Assigning an alternate track explicitly
will generally be required when a track becomes defective subsequent to
disk initialization or when an intermittently bad track is missed during
disk initialization.
The IBCDASDI program cannot check to see if the 3330, 3340, or 3350 space to be initialized was previously formatted.
If you format only five cylinders of a 5-cylinder virtual disk of a
3330, 3340, or 3350 but specify 20 cylinders to be initialized (CYLNO=20), the IBCDASDI program does not initialize all 20 cylinders
but merely updates the format 5 DSCB in the VTOC to indicate available space, without for the existence of 20 cylinders and without
issuing an error message. Later, any attempt to use the sixth through
the twentieth cylinder causes a Seek Check and the channel program abnormally terminates. When assigning alternate tracks explicitly, IBCDASDI aust find a !glig OS Format 4 label on the disk. If this label has been destroyed (ty CMS Format, for example), or if the label does not apply to the
present disk in its present state (for example, a no longer applicable OS Format 4 label might have been restored to the disk by the DDR
utility), then IBCDASDI must be used to perform the disk formatting function before alternate tracks can be assigned= The reco •• ended
procedure in this case is to: Dump the entire disk to tape using the DDR utility Format the disk using IBCDASDI Assign the additional alternate tracks using IBCDASDI Restore the data to the disk from the tape using the DDR utility IOn the 2305 drum, defective tracks should be rewired to alternate
tracks by the CE rather than being flagged and assigned an alternate in
the usual manner. In this case the fact that a track is defective and
has an alternate wired in is transparent to all programming. (CP itself has no recovery procedures for "software assigned" alternate
tracks on the 2305; however, an operating system running in one of its
virtual machines might make use of +.hem.) Section 4. VM/310 Service Programs 181
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