HP StorageWorks XP24000 Continuous Access Software User and Reference Guide, v01 (T5278-96002, June 2007)

suspended, the tracks which contain the following records a re marked in the differential data as modified
(to
be copied during the pairresync operation):
• The rec ordsets that were created by the MCU, but not yet sent to the RCU. After marking these
P-VOLtracksasmodified, the MCU discards these recordsets.
• The re cordsets that were sent to the RCU, but not acknowledged by the RCU. The MCU marks
these P-VOL tracks as modified and discards these recordsets. This ensures that recordsets lost
during transmission to the RCU are identified and marked.
• The recordsets that reached the RCU, but have not yet been settled. After marking these S-VOL
tracks as modified, the RCU discards these recordsets.
• The P -VOL records updated by host-requested write I/Os after the pair was suspended (same
function as for Continuous Access Synchronous pairs).
If a recordset is lost in transmission from the MCU to the RCU, the MCU’s differential data ensures that
the
missing recordset is marked. After the MCU sends the recordset to the RCU, the MCU does not
remove the sidefile entry for the recordset from its cache until it receives an I/O completion signal
(device end) from the RCU.
Table 9 on page 32 describes Continuous Access Asynchronous suspension conditions and indicates
which CU detects the condition and which pairs a re suspended. The Continuous Access offloading timer
option and timeout group options (see “Changing the Consistency Group Options”onpage86) are
used to control the Continuous Access Asynchronous suspension conditions. See Table 29 on page 141
for troubleshooting information for Continuous Access Asynchronous suspension conditions.
Table 9 C ontinuous A ccess Asynchronous Suspension Conditions
Suspension Condition Detected
by:
Continuous Access
Asynchronous Pairs to be
Suspended
TheMCU couldnot sendapending recordsettothe
RCU before the offloading timer async option expired.
MCU
All Cont
inuous
Access
Asynchr
onous pairs with P-VOLs in
the MCU.
During an MCU power-on, the MCU could not
establish communications with the RCU before the
Time Out (RCU Ready) group o ption expired.
MCU
All Continuous Access
Asynchronous pairs with P-VOLs in
the MCU.
The RCU could not settle a pending recordset before
the
Time Out (Copy Pending) group option expired.
RCU
All Continuous Access
Asynchronous S-VOLs in the
consistency group.
The RCU could not communicate with the MCU before
the
Time Out (Copy Pending) group option expired
(see
Changing the Consistency Group Options on
page 86).
RCU
All Continuous Access
Asynchronous S-VOLs in the
consistency group.
The RCU could not receive the recordset successfully
due
to a hardware failure.
RCU
Only the affected S-VOL.
The RCU detected a logical error while selecting the
recordset to be settled.
RCU
All Continuous Access
Asynchronous S-VOLs in the
consistency group or only the
affected S-VOL, depending on the
type of failure and the error level
pair
option.
The RCU could not settle the recordset due to a
hardware failure, track condition, or logical error.
RCU
Interoperability with Other Products a nd Functions
Some types of volumes used by non-Continuous Access and non-Continuous Access Asy nchronous
functions can also be used as a P-VOL and S-VO L of Continuous Access and Continuous Access A sync.
Table 10 on page 33 explains whether non-Continuous Access and non-Continuous Access Asynchronous
volumes are also usable as Continuous Access and Continuous Access Asynchronous volumes.
32
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