Data Areas Track Zero This section describes the data areas used by the IBCDASDI Virtual Disk Initialization
Program. The data areas are: Unit Control Block
TRACK ZERO >
HA RO Rl R2 R3 R4 1< > L--V V V V V V Home Track IPt Record 1Pt Standard Additional
Address Description or Dummy Bootstrap Volume Volume Label
Label (Optional) Figure 1-3. IBCDASDI Track Zero
12 IBM VM/370 Service Routines Program Logic
>
< Rl0 > V J
Additional
Vclume Label (Cptional)
UNIT CONTROL BLOCK
The field UCBREG contains the address of
the UCB. All references to fields in the UCB are made using offsets from UCBREG; the UCE fields are not late led in the IBCDAStI program. The format of the UCE is:
o 4 8 10 *1
*2 11 I 15 I not used 12 I CAW Channel and unit numrer Interrupt PSW Interrupt CSW 1--------------------------------------------------------------- 18 20 o 0 1 1
2 2 4 4
5 5
8 8 10 16
18 24 20 32 Sense Information 2305, 3330, 3340, 3350 Sense Information
Field *,--- unit reference number Not used
Channel and unit number
*2 CAW protect CAW Interrupt PSW Interrupt CSW Sense Information 2305, 3330, 3340, 3350 Sense Information
Figure 1-4. Unit Control Block
Chapter i. IBCDASDI--The Virtual Disk Initialization n .... ____ _ r ... ... o.w 13
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