HP StorageWorks XP Remote Web Console Software - Manual (Page 132)

merged at the MCU. This option is available only when the selected volume is an XP
Continuous Access P-VOL.
◦ Disable: The S-VOL of this pair only accepts read I/Os while the pair is split.
•
Suspend Kind (default = S-VOL):
S-VOL: The P-VOL accepts all subsequent write I/O operations, and the MCU keeps track
of updates while the pair is split. Subsequent write I/O operations to the P-VOL will be ◦
accepted or rejected depending on the fence level of the pair. This setting is available
from the MCU and RCU and should be used if you need to keep the P-VOL online. All XP
Continuous Access Asynchronous pairs have this setting.
◦ P-VOL Failure (available only for XP Continuous Access Synchronous and only when
connected to the MCU): The MCU will reject all write I/O operations to the P-VOL while
the pair is split, regardless of the P-VOL fence level setting. This setting should be used if
you need to maintain synchronization of the XP Continuous Access pair.
•
Asynchronous Parameters:
Suspend Range: Group or LU. Default = Group when one pair in each group is selected.
Default = Volume when two or more pairs in a group are selected.
Group: All pairs in the same consistency group(s) as the selected pair(s) will be split. You
must select only one pair in each consistency group.
◦
LU: Only the specified pair(s) will be split if the error level of the pair is Group.
For the LU suspend range setting, if you select pairs with PAIR status and other than PAIR
status in the same consistency group, an unexpected suspend may occur during the pair
operations (Pairsplit-r, Pairsplit-S, and Pairresync) under heavy I/O load conditions. You
can estimate whether or not the I/O load is heavy from the rate of sidefile cache (around
30%) or if you cannot see the sidefile cache rate from the frequency of host I/O. The
suspend pair operations should be performed under light I/O load conditions.
◦ Pending Update: Drain or Purge (default = Drain).
Drain: As soon as the RCU accepts the Pairsplit-r operation, the RCU will finish settling
all pending recordsets for the pair. After settling all pending recordsets, if there are no
recordsets for a fixed period of time, the MCU will change the pair status from Suspending
to PSUS.
If there is no period of time without recordsets (that is, recordsets continue to be generated),
the RCU will discontinue the original pairsplit-r operation and forcibly suspend the pair.
Purge: The MCU changes the pair status from Suspending to PSUS as soon as the RCU
accepts the pairsplit-r operation. The MCU and RCU discard all pending recordsets and
mark the cylinders/tracks that contain discarded recordsets as modified in the P-VOL and
S-VOL bitmaps, respectively. When the pair is resynchronized (pairresync), the P-VOL
and S-VOL bitmaps will be merged at the MCU, and all cylinders/tracks marked as
modified will be copied to the S-VOL.
If the MCU does not receive acknowledgement of the pairsplit-r operation from the RCU
within the Copy Pending Timeout setting, the MCU will forcibly suspend all affected XP
Continuous Access Asynchronous pairs.
If you select a pair from the volume list and change the settings, and if you use a
drop-down list to set blank to a parameter, the parameter takes the default value for each
pair. If you select the settings from the preview list before applying the changed settings,
and if you use a drop-down list to set blank to a parameter in the Pairsplit-r dialog box,
the parameter value in the preview list will not be changed.
To split one or more XP Continuous Access pairs:
132 Performing XP Continuous Access Pair Operations