Hitachi ShadowImage for IBM z/OS User"s Guide (T5213-96002, June 2007)

3-6 Preparing for ShadowImage™ for z/OS
®
Operations
Hitachi ShadowImage™ for IBM
®
z/OS
®
User’s Guide
– ShadowImage
– Compatible FlashCopy Version 1
– Compatible FlashCopy Version 2
– Volume Migration
– Copy-on-Write Snapshot
• Program products using pair tables
– ShadowImage for z/OS
– Compatible FlashCopy Version 1
– Volume Migration
If ShadowImage for z/OS and these program products are used in the same
storage system, the number that is deducted the number of differential tables
and pair tables used by the pairs (migration plans in case of Volume Migration)
of the program products shown in above from the number of differential tables
and pair tables in the whole storage system will be the number of available
differential tables and pair tables for SIz pairs.
For information about how to calculate the number of differential tables and
pair tables that are required for ShadowImage, see the ShadowImage Guide,
and as for Compatible Mirroring for IBM FlashCopy Version 1 and Compatible
Mirroring for IBM FlashCopy Version 2, see the Compatible FlashCopy User’s
Guide. Also, see the Performance Manager User’s Guide to calculate the
number of differential tables and pair tables that are required for Volume
Migration, and see the Copy-on-Write Snapshot User’s Guide to calculate the
number of differential tables that are required for Copy-on-Write Snapshot.
Assuming that only ShadowImage for z/OS uses differential tables and pair
tables, this section describes how to calculate the number of differential tables
and pair tables required for one SIz pair, and the conditions you need to
consider when calculating the number of SIz pairs that can be created.
• 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 3-3)
(Z): 20,448 (The number of the slots that can be managed by a differential
table)
Note that you should 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...