Data Areas
This section contains descriptions of the
DASD record fermats and the layout of these
DASD records fer: • 2305 Models 1 and 2 • 2314/2319 devices • 3330 series • 3340 series • 3350 series
Record 0 is the standard 8-byte data area, set to 0 except fer cylinder O. On cylinder 0, pages are flagged
as For 2305, 2314/2319, 3330, 3340, and 3350 in compatil:ility
lIode: .-- I I EO 00 00 00 00 00 cc CO I I For 3350 in native mode only: FO 00 00 00 00 00 00 OC Figure 3-3. Record 0 Format Chapter 3. The Format Service Program 71

24 bytes track 0 cylinder 0 1PL record -puts system into wait state if storage device is loaded (via IPt function).
f 1 100 02 00 00 00 00 00 00 03 00 00 00 20 00 00 CO 00 00 00 00 00 00 00 001 '--- J
Figure 3-4. Record 1 For.at l 4096 bytes - track 0 cylinder 0 Checkpoint record -this is the Checkpoint prograa load at V8/370 1Pt ti.e to retrieve and save control inforaation for a war. start.
Figure 3-5. Record 2 Format 1 consists of a 4-byte key and an aO-byte record.
Key Data
, I I Pointer key I Key I Label FO to VTOC 00 40 00 CP370 40 pointer
to user I I I I Directory I .J 0 3 0 4 10 11 16 21 41 46 51 52
Figure 3-6. Record 3 Format
72 IBM VM/370 Service Routines Program Logic
i I 401 I I 56 79