HP StorageWorks Continuous Access XP user guide for the XP10000/XP12000 (December 2005)

30 Continuous Access XP for the XP10000/XP12000
Continuous Access XP Asynchronous suspension conditions
Continuous Access XP Asynchronous operations involve additional suspension conditions related to
recordset operations. The MCU and RCU detect Continuous Access XP Async suspension conditions and
suspend Continuous Access XP Async pairs. When a Continuous Access XP Async pair is suspended,
cylinders containing the following records are marked in the cylinder bitmap as modified (to be copied
during the pairresync operation):
• Recordsets created by the MCU, but not yet sent to the RCU. After marking these P-VOL cylinders as
modified, the MCU discards these recordsets.
• Recordsets sent to the RCU, but not acknowledged by the RCU. The MCU marks these P-VOL cylinders
as modified and discards these recordsets, ensuring that recordsets lost during transmission to the RCU
are identified and marked.
• Recordsets that reached the RCU, but have not yet been settled. After marking these S-VOL cylinders as
modified, the RCU discards these recordsets.
• P-VOL records updated by host-requested write I/Os after the pair was suspended (same function as for
Continuous Access XP Synchronous pairs).
If a recordset is lost in transmission from the MCU to the RCU, the MCU’s cylinder bitmap ensures 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 describes Continuous Access XP Asynchronous suspension conditions and indicates which CU
detects the condition and which pairs are suspended. The Continuous Access XP offloading timer option
(see ”Asynchronous copy option” on page 80) and timeout group options (see ”Modifying consistency
group options (CT Group Option)” on page 78) control Continuous Access XP Asynchronous suspension
conditions. For more information about Continuous Access XP Asynchronous suspension conditions, see the
Troubleshooting chapter of the HP StorageWorks Command View XP User Guide for XP Disk Arrays or the
HP StorageWorks XP Remote Web Console User Guide for XP12000/XP10000.
Table 9 Continuous Access XP Asynchronous suspension conditions
Suspension condition Detected by Continuous Access XP ASYNC pairs to
be suspended
The MCU could not send a pending recordset to
the RCU before the offloading timer async option
expired.
MCU
All
Continuous Access XP ASYNC pairs
with P-VOLs in the MCU.
During MCU power-on, the MCU could not
establish communications with the RCU before the
RCU ready timeout group option expired.
MCU
All
Continuous Access XP ASYNC pairs
with P-VOLs in the MCU.
The RCU could not settle a pending recordset
before the copy pending timeout group option
expired.
RCU
All
Continuous Access XP ASYNC S-VOLs
in the consistency group.
The RCU could not communicate with the MCU
before the copy pending timeout group option
expired (see ”Modifying consistency group
options (CT Group Option)” on page 78).
RCU
All
Continuous Access XP ASYNC 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 XP ASYNC S-VOLs in
the consistency group or only the affected
S-VOL, depending on type of failure and
error level Continuous Access XP ASYNC
pair option.
The RCU could not settle the recordset due to a
hardware failure, track condition, or logical error.
RCU