HP Hitachi ShadowImage for Mainframe User Guide (T5213-96032, November 2011)

• The capacity of each volume used to create a pair (this is the capacity specified as the CVS
or customized volume size)
Use the following expression to calculate the total number of the differential tables and pair
tables per pair.
Total number of the differential tables per pair = ((X) + (Y)) × 15 ÷ (Z)
(X): The number of the cylinders of the volume
(Y): The number of the control cylinders (see Table 15 (page 45))
(Z): 20,448 (The number of the slots that can be managed by a differential table)
Round up the number to the nearest whole number. For example, in case of a volume which
emulation type is 3390-3, and when provided that the number of the cylinders of the divided
volume is 3,390 ((X) in the expression above), the calculation of the total number of the
differential table is as follows.
(3,339 + 6) × 15 ÷ 20,448 = 2.4537...
When you round up 2.4537 to the nearest whole number, it becomes 3. Therefore, the total
number of the differential table for one pair is 3 when emulation type is 3390-3.
You may use 36 differential table per one pair table. Therefore, the total number of the pair
tables is 1 when emulation type is 3390-3. For example, if the emulation type is 3390-M and
the number of the cylinders of the volume is the default value, the number of pair tables is 2.
However, only the emulation type 3390-M can be used, if you use plural pair tables on a
mainframe system.
Table 15 (page 45) shows the number of the control cylinders according to the emulation
types.
Table 15 Number of the Control Cylinders According to the Emulation Types
Number of the Control CylindersEmulation Type
73380-3
73380-3A
73380-3B
73380-3C
223380-F
73380-K
73380-KA
73380-KB
73380-KC
63390-3
63390-3A
63390-3B
63390-3C
63390-3R
253390-9
253390-9A
253390-9B
253390-9C
Assessing ShadowImage for Mainframe Requirements 45