!2I All For example, the 3330 track format for all formatted cylinders except
cylinder 0 is shown in Figure Track 0: RO R1 R2 R3 I I I !I I 8 bytes 4096 bytes 4096 bytes 4096 bytes
Track 1 to Track 18: RO R1 R2 R3
1
8 bytes 4096 bytes 4096 bytes 4096 bytes
igure 7. For.at of 3330 Cylinders for Use by CP All volumes containing space for CP use (paging, spooling, and so on)
must have a properly formatted cylinder O. The only service progra.
that can do this is the For.at/Allocate progra. Cylinder 0 is formatted like other cylinders except that the space
associated with the first three 4096-byte blocks is reserved for system
use. This area is then formatted as illustrated in Figure 8.
Track 0 RO R1 R2 KEY R3
, , \(j r I IPL I DMKCKP I I V I I rec I !odule I 101 VOLID II ILl 8 24 4096 111 4 80 R4 KEY RS KEY R6 FH I , .--- / /----, Allocation I I For.at 1 I For.at I I Byte .ap I I 4 DSCB I I 5 DSCB I I L--//----J 1024 44 96 44 96
Track 1 to Track 18 are the same as the nonzero cylinders.
Figure 8. 3330, 3340, or 3350 Cylinder 0 For.at
Section 4. V8/370 Service Prograas 173

The contents of each record in cylinder 0 track 0 are as follows: RO Nothing. R1 IPL record -- Puts the system into wait state if storage volume is
loaded before CP nucleus is built.
R2 Checkpoint record
for a warm start. Used by CP to save and retrieve inforaation
R3 Voluae label -- Same as OS VOL1 label. On CP systea residence volume, area in data record marks the beginning of the system directory. A label is automatically written when cylinder 0 is formatted. The owner field of the label record contains "VB/310" if there is allocation data present in R4.
R4 Allocation Byte Map Bach byte identifies a cylinder and
specifies its usage (paging, spooling I directory, and so on). This aap is filled in by the ALLOCATB function of the D!KF!T service
program.
RS Foraat 4 as DSCB type label --For compatibility with os. Also,
the IBCDASDI prograa uses this label to keep a record of how aany alternate tracks remain available for assignment on this disk. The
Format/Allocate program will preserve this information by first
reading it fro. any existing Foraat 4 label, and then writing it
back in the new label.
R6 Format S OS DSCB type label For coapatibility with as. Label
indicates to os that no space is available cn this voluae.
FR Is one or more filler records.
Format/Allocate program control statements may be supplied in card form via a card reader, or may be entered at the system console. All error messages regarding improper specification of control statements
are displayed at the console. FORHAT/ALLOCATB PROGRAH CIRD INPUT Punch control statements for card input
field is separated from the adjacent field
row cause the insertion of a default value.
the insertion of two default 114 VM/310 OFerator's Guide
start in coluan 1, and each by a comma. Two co •• as in a
Three commas in a row cause