HP StorageWorks XP Remote Web Console Software - Manual (Page 110)

The Minimum Paths option allows you to specify the minimum number of paths required for each
RCU connected to the current MCU (default = 1). If the number of paths falls below this number,
the MCU suspends all affected TrueCopy for Mainframe (and XP Continuous Access) pairs to
prevent hosts from adversely affecting performance due to the inadequate number of paths. If the
MCU contains TrueCopy for Mainframe pairs which contain critical data for disaster recovery, set
the minimum number of paths to one, so that TrueCopy for Mainframe operations continue even
if there is only one path to an RCU. If you need high performance at the MCU, set the minimum
number of paths to two or more (up to eight per CU), depending on the number of pairs managed
by the MCU.
When you have TrueCopy for Mainframe Async pairs configured on Fibre Channel interface, set
the same value for the Minimum Paths option for all RCUs.
The RCU options are common to both TrueCopy for Mainframe and TrueCopy operations. The
most recently entered Minimum Paths value (entered on TrueCopy for Mainframe or XP Continuous
Access RCU Option dialog box) will be applied to both TrueCopy for Mainframe and XP Continuous
Access operations
CAUTION: If TrueCopy for Mainframe pairs are suspended because the number of paths has
dropped below this setting, the M-VOL fence level pair option determines whether the TrueCopy
for Mainframe Sync M-VOLs are fenced (for example, reject all write operations).
The RIO MIH Time setting specifies the time value for the remote I/O (RIO) missing interrupt handler
(MIH), which is the wait time until data transfer from the MCU to RCU is complete. The RIO MIH
time value must be from 10 to 100 seconds. The default setting is 15 seconds.
The Incident of RCU option allows you to specify which host(s) the RCUs will report link incident
records to. When to any host is selected, the RCUs will send link incident records to all RCU hosts
and to all MCU hosts. When only to RCU host is selected, the RCUs send link incident records only
to the RCU host(s). Make sure that RCU link incidents are reported to the proper host(s) so that
corrective action, if needed, can be taken. The to any host setting is recommended when TrueCopy
for Mainframe is being used for disaster recovery purposes.
The FREEZE Option setting allows you to enable or disable support for the CGROUP (FREEZE/
RUN) PPRC TSO command. The FREEZE option is available only when PPRC support = Yes. If you
select Enable, the MCU will accept and perform the CGROUP command. If you select Disable, the
MCU will reject the CGROUP command.
Enable the FREEZE option only after all MCU-RCU paths have been added.
The PPRC commands do not allow you to change the RCU options.
The Round Trip Time setting is a reference value used for automatic control of the initial copy pace
and for avoiding remote I/O response time to the update I/Os being affected by initial copy while
the copy operation is in progress. The value of Round Trip Time is compared with the remote I/O
response time, and then, the copy pace is controlled when the difference between the two values
is large.
If the difference between the remote I/O response time and the value of Round Trip Time is large,
for example, the remote I/O response time is 500 ms but the value of Round Trip Time is 1 ms,
the copy pace will decrease or sometimes the initial copy will interrupt, so that the initial copy
process does not occupy the entire bandwidth of the line(s).
On the other hand, if the difference between the remote I/O response time and the value of Round
Trip Time is small, for example, the remote I/O response time is 5 ms and value of Round Trip
Time is 1 ms, the initial copy runs at specified pace.
The setting of the Round Trip Time is available for the initial copy operation of TrueCopy for
Mainframe and TrueCopy for Mainframe Async on the XP24000/XP20000 disk arrays and their
successor models.
The default value of Round Trip Time is 1 ms. Specify an appropriate value for Round Trip Time if
the distance between the MCU and RCU is long or if there is a delay caused by line equipment.
110 Performing TrueCopy for Mainframe Configuration Operations