HP StorageWorks XP24000/XP20000 Continuous Access Software User Guide (T5278-96049, November 2011)
• 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 XP 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 13 (page 36) describes XP Continuous Access Asynchronous suspension conditions and
indicates which CU detects the condition and which pairs are suspended. The XP Continuous
Access offloading timer option and timeout group options (see “Changing the Consistency Group
Options” (page 102)) are used to control the XP Continuous Access Asynchronous suspension
conditions. See “Resolving XP Continuous Access Asynchronous Suspension Conditions” (page 156)
for troubleshooting information for XP Continuous Access Asynchronous suspension conditions.
Table 13 XP Continuous Access Asynchronous Suspension Conditions
XP Continuous Access Asynchronous
Pairs to be Suspended
Detected by:Suspension Condition
All XP Continuous Access Asynchronous
pairs with P-VOLs in the MCU.
MCUThe MCU could not send a pending recordset to the RCU
before the offloading timer async option expired.
All XP Continuous Access Asynchronous
pairs with P-VOLs in the MCU.
MCUDuring an MCU power-on, the MCU could not establish
communications with the RCU before the Time Out (RCU
Ready) group option expired.
All XP Continuous Access Asynchronous
S-VOLs in the consistency group.
RCUThe RCU could not settle a pending recordset before the Time
Out (Copy Pending) group option expired.
All XP Continuous Access Asynchronous
S-VOLs in the consistency group.
RCUThe RCU could not communicate with the MCU before the
Time Out (Copy Pending) group option expired).
Only the affected S-VOL.RCUThe RCU could not receive the recordset successfully due to
a hardware failure.
All XP Continuous Access Asynchronous
S-VOLs in the consistency group or only
RCUThe RCU detected a logical error while selecting the recordset
to be settled.
the affected S-VOL, depending on the
RCUThe RCU could not settle the recordset due to a hardware
failure, track condition, or logical error.
type of failure and the error level pair
option.
Interoperability with Other Products and Functions
Some types of volumes used by non-XP Continuous Access and non-XP Continuous Access
Asynchronous functions can also be used as a P-VOL and S-VOL of XP Continuous Access and XP
Continuous Access Asynchronous. Table 14 (page 36) explains whether non-XP Continuous Access
and non-XP Continuous Access Asynchronous volumes are also usable as XP Continuous Access
and XP Continuous Access Asynchronous volumes.
Table 14 Whether Non-XP Continuous Access and Non-XP Continuous Access Asynchronous Volumes
Can Be Used as XP Continuous Access and XP Continuous Access Asynchronous Volumes
Can the Volumes be
Used as XP
Can the Volumes be
Used as XP
Can the Volumes
be Used as XP
Can the Volumes be
Used as XP
Functions and Volumes
Continuous AccessContinuous AccessContinuous Access
S-VOL?
Continuous Access
P-VOL? Asynchronous
S-VOL?
Asynchronous
P-VOL?
LUN Expansion (LUSE)
YesYesYesYesLUSE Volume
36 About XP Continuous Access Operations