Hitachi TrueCopy for z/OS (T1711-96009, June 2006)
TrueCopy for z/OS user guide 49
Cache, NVS, and DASD Fast Write
Cache and nonvolatile storage (NVS) must be operable for both the MCU and RCU of a TC390 volume
pair. If not, the Add Pair operation will fail. The remote disk array cache should be configured to
adequately support the TC390 remote copy workloads as well as any local workload activity.
DASD fast write (DFW) is required at the MCU and RCU only when the DFW-to-R-VOL required TC390
pair option (see ”Creating TrueCopy Volume Pairs (Add Pair)” on page 121) is specified. If DFW to an
R-VOL is blocked and the TC390 pair was established with the DFW-to-R-VOL required pair option, the
MCU detects DFW OFF at the R-VOL and suspends the pair. TC390 pairs that were established using PPRC
commands use the default value of not required and therefore are not suspended when DFW to the R-VOL
is blocked.
NOTE: The DFW to R-VOL setting does not affect the I/O performance of the M-VOLs. If one side of
cache is closed due to an RCU failure, the TC390 copy operation still uses DFW. The only difference
between not required and required is that new pairs cannot be established with the DFW-to-R-VOL
required option when one side of RCU cache is closed (the add pair operation fails).
Consistency Groups
The TC390A consistency groups have the following requirements:
• All TC390A pairs must be assigned to one and only one consistency group.
• The maximum number of volume pairs in one consistency group is 4,096 (entire RCU).
• The maximum number of consistency groups established for one MCU-RCU pair is 128. The RCU
supports a maximum of 128 groups. This limit of 128 groups includes both TC390A groups and TC
Asynchronous groups (for example, 64 TC390A + 64 CA Asynchronous).
• Each update I/O to the M-VOLs in one consistency group must be time-stamped using a common timer
facility. The primary host system cannot access volume pairs of the same consistency group if the pairs
do not have a common timer reference.
• A consistency group must consist of TC390A pairs or CA Asynchronous pairs, but not both.
• Only TC390A pairs that belong to the same CLPR can be allocated to one consistency group. For
further information on CLPR, please refer to the HP StorageWorks Command View XP User Guide for XP
Disk Arrays or the HP StorageWorks XP Remote Web Console User Guide for the specific disk array.
Installing the TrueCopy Hardware
Initial installation of the TC390 hardware is planned and performed by the user and the HP representative.
To install the hardware required for TC390 operations:
1. User: Identify the TC390 M-VOLs and R-VOLs (main and remote volumes) so that the TC390 hardware
can be installed and configured properly.
2. User: On the host operating system, verify that the missing interrupt handler (MIH) value (also called
host I/O patrol time) is set high enough to accommodate the number of volume pairs, the cable length
between the MCUs and RCUs, and the initial copy pace. The recommended MIH value for TC390
operations is 60 seconds. For MVS, the MIH value is specified in the SYS1.PARMLIB file.
NOTE: The recommended MIH value for HXRC is different than for TC390. If you are performing
TC390 and HXRC on the same XP1024/XP128/XP12000/XP10000 (or other XP disk arrays) at
the same time, contact your HP account support representative for assistance.
3. User and HP Representative: Install the Command View XP management station near the TC390
MCU(s) and connect the Command View XP management station to the TC390 MCU(s) through the
LAN. HP recommends that you also install a Command View XP management station connected to the
RCUs at the remote site.
4. HP Representative: Enable TC390 on all MCUs and RCUs. Verify that the cache, NVS, and DFW of the
MCUs and RCUs are properly configured for TC390 operations. See ”Cache, NVS, and DASD Fast
Write” on page 49. If the user plans to perform TC390A and/or HXRC operations in the same disk