The following tables show how much space VSAM uses for various DASDs. See Table 1 for the physical characteristics of DASDs.

Use these charts to select control interval sizes that make the most efficient use of storage. Refer to Control interval size for selected devices to determine if the control interval size is equal to the physical block size of the data component.

Remember that the physical block size for the data component may be different from the physical block size for the index component, even if the same control interval size is selected for both. Thus, while the physical block size for the index component is always equal to the control interval size, the physical block size for the data component may be smaller than the control interval size. Multiple physical blocks may compose one control interval for the data component.

For example, if a facility is using the 3390 DASD and a control interval size of 14336 is selected for both the index and data components, then the index component will have a physical block size of 14336 (one physical block per control interval) and the data will have a physical block size of 7196 (two physical blocks per control interval).

If the exact block size is not listed, see the appropriate Direct Access Storage Reference Summary.