Continuous Access Xp Suspend Types - HP xp12000 User Manual

When a Continuous Access XP Sync pair is suspended, the MCU stops performing update copy operations
to the S-VOL and may or may not continue accepting write I/Os for the P-VOL, depending on the P-VOL
fence level pair option. If a synchronous update copy operation fails, the MCU maintains exact
synchronization by reporting a unit check and decommitting the P-VOL update. The host system and
application program regard that write operation to the P-VOL as failed. If the MCU accepts write I/Os for
a suspended P-VOL, the MCU tracks P-VOL cylinders updated while the pair is suspended. When a
suspended sync pair is resumed, the MCU copies out-of-sync P-VOL cylinders to the S-VOL. Continuous
Access XP does not allow access to an S-VOL while the pair is suspended (only when split).
You must stop host I/Os before suspending Continuous Access XP Synchronous pairs with the Data fence
level and following conditions:
• Continuous Access XP Synchronous and Asynchronous pairs exist in the same disk array
• There are host I/Os to the Continuous Access XP Asynchronous pairs
If you do not stop host I/Os, pairs might be forcibly suspended because of a time-out error, and host I/Os
are rejected.
When a Continuous Access XP Asynchronous (Continuous Access XP Async) pair is suspended, the MCU
stops performing Continuous Access XP Async recordset operations for the pair. The MCU continues
accepting write I/Os for the suspended P-VOL and tracks P-VOL cylinders updated while the pair is
suspended. The MCU and RCU also tracks recordsets discarded during the pair suspension. When a
suspended Continuous Access XP Async pair is resumed, the RCU sends the S-VOL cylinder bitmap to the
MCU, and the MCU merges the P-VOL and S-VOL bitmaps to determine which cylinders are out-of-sync.
This method ensures that all cylinders containing recordsets discarded at the RCU are resynchronized at
this time.
A suspended (or split) Continuous Access XP Async S-VOL has an additional status called consistency
status. Consistency status is displayed only at the RCU and indicates the S-VOL's update sequence
consistency with respect to other S-VOLs in the same group. See
consistency status for suspended/split Continuous Access XP Async S-VOLs.
Table 9

Continuous Access XP suspend types

Type Applies to
PSUE, P-VOL, S-VOL
by RCU
PSUE, P-VOL, S-VOL
S-VOL Failure
PSUE, P-VOL, S-VOL
MCU IMPL
PSUE, P-VOL, S-VOL
Initial Copy Failed
PSUE, S-VOL
Continuous Access
MCU P/S OFF (
XP
PSUS, P-VOL, S-VOL
Sidefile overflow
Continuous Access
(
XP
Async only)
Description
The MCU detected an error condition at the RCU causing the MCU
to suspend the Continuous Access XP volume pair. S-VOL suspend
type is PSUE-S-VOL Failure.
The MCU detected an error during RCU communications or update
copy. In this case, S-VOL suspend type is usually PSUE-S-VOL
Failure. This suspend type is also used when the number of paths
falls below the minimum number of paths setting on the RCU
Option pane.
The MCU could not find valid control information in its nonvolatile
memory during IMPL. This condition occurs only if the MCU is
without power for more than 48 hours (power failure and fully
discharged backup batteries).
The Continuous Access XP pair was suspended before the initial
copy operation was complete. Data on the S-VOL is not identical to
data on the P-VOL.
The RCU received a request from the MCU to suspend the S-VOL
due to MCU power-off. The RCU stops expecting recordsets from
Async only) that MCU. The P-VOL status does not change due to MCU
power-off.
The amount of sidefile exceeds the specified "current pending
update data rate," and the RCU data is not transferred within the
specified "offloading timer."
Continuous Access XP user guide for the XP12000/XP10000
Table 8 on page 28 for a description of
29