HP XP Business Copy Software - Manual (Page 18)

18 ShadowImage for the XP1024/XP128/XP12000/XP10000/SVS 200
Requirements on the Maximum Number of Pairs
The number of pairs you can create depends on the emulation type and the capacity of the paired
volumes. For details, refer to the following table that shows the number of pairs that can be created with
volumes of each emulation type and capacity.
Use the following expression to calculate the total number of the differential tables per pair:
Total number of the differential tables per pair = ( (X) + (Y) ) x 15 ÷ (Z)
(X): Number of the cylinders of the volume that is divided at arbitrary size.
(Y): Number of the control cylinders (see
Table 3 ).
(Z): Number of slots that can be managed by a differential table.
(1,916 x 32)
Round up the number to the nearest whole number. For example, in case of a volume for which the
emulation type is 3390-3 and the number of cylinders of the divided volume is 3,390 ((X) in the preceding
expression), the calculation of the total number of the differential table is as follows:
(3,390 + 6) x 15 ÷ (1,916 x 32) = 0.81836
When you round up 0.81836 to the nearest whole number, it becomes 1. Therefore, the total number of the
differential table for one pair is 1 when emulation type is 3390-3.
The following table shows the number of the control cylinders according to the emulation types.
Cache maintenance If XP1024/XP128/XP12000/XP10000/SVS 200 cache maintenance is performed
during a period of high I/O usage, one or more SI390 pairs may be suspended.
Reduce the I/O load before cache maintenance.
Failures When a failure of any kind prevents an SI390 copy operation from completing, the
pair is suspended. If an LDEV failure occurs, the pair is suspended. If a PDEV failure
occurs, SI390 pair status is not affected because of the RAID architecture.
Maintenance/Update When the disk array maintenance is performed, or the microprogram is updated,
you may have to recreate your SI390 pairs again.
Table 2 ShadowImage for z/OS requirements (continued)
Parameter Specification
Table 3 The Number of the Control Cylinders According to the Emulation Types
Emulation Type Number of the Control Cylinders
3380-3 7
3380-3A 7
3380-3B 7
3380-3C 7
3380-F 22
3380-K 7
3380-KA 7
3380-KB 7
3380-KC 7
3390-3 6
3390-3A 6
3390-3B 6
3390-3C 6
3390-3R 6