Disk Volume Layout Examples

The examples show in what arrangement IOCS writes labels on volumes, cylinders, and tracks on output. IOCS expects labels to be so arranged on input. Each of the examples shows:
  • How the space on the volume is used (cylinder distribution).
  • The layout of the track with volume labels and VTOC.

Some of the examples give the contents of extent fields of the first format-1 label and the format-4 label in the VTOC.

The examples are:
  • A CKD volume of 410 cylinders with the VTOC beginning on track 1 of cylinder 100 – Figure 1.
  • A CKD volume of 202 cylinders with disk files that have user-standard labels – Figure 2.
  • A multivolume VSAM layout showing the relationship between the labels, the catalog, the data space, and the files – Figure 4.

Figure 1. Disk Volume Layout: One File plus VTOC

Figure 2. Disk Volume Layout: Files with User-Standard Labels - Part 1
Figure 3. Disk Volume Layout: Files with User-Standard Labels - Part 2

Figure 4. Disk Volume Layout with VSAM Data Spaces
Volume Layout 
                           Volume 1
 ┌──────┬──────────────┬──────────────┬──────────────┬──────────────┐
 │ VTOC │ Data Space 1 │ VSAM Catalog │ Data Space 1 │ Data Space 2 │
 └──────┴──────────────┴──────────────┴──────────────┴──────────────┘
          File A File B                 Free Space       File C *
 
                           Volume 2
 ┌──────┬──────────────┬──────────┬──────────┬──────────────┐
 │ VTOC │ Data Space 3 │ SAM File │ DAM File │ Data Space 3 │
 └──────┴──────────────┴──────────┴──────────┴──────────────┘
             File D                               File E
VTOC Layout 
                          Volume 1
 ┌───────┬──────────┬───────────────────────────────────────┐
 │       │          │    IBM Standard File Labels for:      │
 │ VTOC  │ Format-5 ├─────────┬──────────────┬──────────────┤
 │ Label │ Label ** │ Catalog │ Data Space 1 │ Data Space 2 │
 └───────┴──────────┴─────────┴──────────────┴──────────────┘
 
                          Volume 2
 ┌───────┬──────────┬───────────────────────────────────────┐
 │       │          │   IBM Standard File Labels for:       │
 │ VTOC  │ Format-5 ├───────────────┬───────────┬───────────┤
 │ Label │ Label ** │ Data Space 3  │ DAM File  │ SAM File  │
 └───────┴──────────┴───────────────┴───────────┴───────────┘
*
A unique file.
**
Not used by VSE.