HP StorageWorks XP Remote Web Console Software - Manual (Page 27)

Hitachi TrueCopy for z/OS user guide 27
R-VOL read option
For additional flexibility, TC390 offers a special R-VOL read option. The HP representative enables the
R-VOL read option on the RCU (mode 20). You can use the TC390 R-VOL read option to read a TC390
R-VOL only while the pair is suspended, without having to delete the pair. The RCU will change only the
VOLSER of the suspended R-VOL so that the R-VOL can be online to the same host as the M-VOL while the
pair is suspended. All other write I/Os will be rejected by the RCU. The MCU copies the M-VOL VOLSER
back onto the R-VOL when the pair is resumed. When the R-VOL read option is not enabled and/or the
pair is not suspended, the RCU rejects all read and write I/Os to a TC390 R-VOL. If you need write access
to an R-VOL, you must delete the pair.
NOTE: For 2105 or 2107 controller emulation, the CSUSPEND command to the R-VOL of a suspended
TC390 pair will be rejected when the TC390 R-VOL read option is used.
Difference management
The differential data (updated by write I/Os during split or suspension) between M-VOL and R-VOL is
stored in each cylinder bitmap. When a deleted/suspended pair is resumed (Resume Pair), the MCU
merges the M-VOL and R-VOL bitmaps, and the differential data is copied to the R-VOL. The unit of data
stored in the bitmap is Track or Cylinder. When adding a pair (Add Pair), you can select Track or Cylinder
and you can also confirm the unit.
When you add a pair with the setting of Track, the number of pairs you can create is restricted. If you
create the pairs more than the restricted number, a pair is automatically added with Cylinder. You can
restrict the automatic change of the setting. Before using this function, contact your HP account support
representative.
The restriction of the number of pairs depends on the capacity of the volumes used for the pairs. Both of the
MCU and RCU are restricted.
The number of bitmap area in the disk array is 10,476. You can calculate the number of bitmap area. If the
calculated bitmap area exceeds the number of bitmap area in the disk array, adding pairs operation is
restricted.
To calculate the number of bitmap area, you can use the following equation:
( ( (Number of Cylinders * 15) / 75,136) ) - 1
Table 5 Operation of the unit of data stored in bitmap
Program The Unit of Data Stored in Bitmap Confirmation
Default (Auto) 1
1. Default (Auto) means that Track or Cylinder is automatically set according to the capacity (number of cylinders or number
of cylinders set by VLL) of the volumes used for the pairs. For volumes that have 10,019 cylinders or more, Cylinder is set.
For other volumes, Track is set.
Track Cylinder
XP Command View
Advanced Edition
Software or XP
Remote Web
Console
Available Available Available Available
PPRC TSO Not available Not available Not available Not available
Table 6 Maximum Pairs by Emulation Type, when pairs are created without custom volumes
Emulation
Type
Number of
Cylinders
Number of
Bitmap Areas
Maximum Number of Pairs
(Added Shared Memory:
1 set)
Maximum Number of Pairs
(Added Shared Memory:
2 sets)
3380-J 885 1 11,605 16,384
3380-E 1,770 1 11,605 16,384