Maximum Number Of Pairs Allowed; Calculating Maximum Number Of Pairs - HP StorageWorks P9000 User Manual

system administrator must take precautions to prevent system problems related to duplicate VOLSERs
(such as defining Continuous Access Journal Z S-VOLs not to come online automatically).
CAUTION: If the volumes that become Continuous Access Journal Z S-VOLs are physically attached
to the same system images as the volumes that become the Continuous Access Journal Z P-VOLs,
the potential for error increases. For example, when a Continuous Access Journal Z pair is released,
the old S-VOL is usually offline. When a host system is IPL'd (initial program loaded), the operator
is offered both volumes and asked which volume should be left offline. You can avoid duplication
of the VOLSER as follows:
1. Identify the volumes that are not accessed by the host system.
2. Perform CHP OFF or some other operation to insure that the volumes are inaccessible.
3. When performing IPL, make sure to perform LOAD CLEAR.

Maximum number of pairs allowed

P9500 has a limit on the number of pairs that can be created. Therefore, it is necessary to calculate
the maximum number of pairs on the P9500 storage system. The maximum number is limited
according to the following:
1. The number of cylinders in the volumes, which must be calculated.
2. The number of bitmap areas required for Continuous Access Journal data and journal volumes.
This is calculated using the number of cylinders.
3. The maximum number of pairs that can be created, calculated using the number of required
bitmap areas.
CAUTION:
Continuous Access Journal Z, Continuous Access Synchronous, Continuous Access Synchronous
Z, and External Storage Access Manager. If you use Continuous Access Journal with Continuous
Access Journal Z, Continuous Access Synchronous, and Continuous Access Synchronous Z, use
the total number of each pair's bitmap areas to calculate the maximum number of pairs. In addition,
if Continuous Access Journal and Continuous Access Synchronous share the same volume, use the
total number of both pairs regardless of whether the shared volume is primary or secondary.

Calculating maximum number of pairs

NOTE: In the calculations below, ceil() indicate that the value between the parentheses should
be rounded up to the nearest integer.
To determine the number of cylinders
The number of cylinders according to the emulation type are listed below.
Table 5 Number of cylinders per emulation type
Emulation type
3380-3
3390-3, 3390-3R
3390-9
3390-L
3390-M
To calculate the number of required bitmap areas:
30 Planning volumes, systems
The bitmap areas that are used for Continuous Access Journal are also used for
Number of cylinders
3,339
3,339
10,017
32,760
65,520