HP XP Continuous Access Software - Manual (Page 27)

Continuous Access XP user guide for the XP1024/XP128 27
Continuous Access XP split types (PSUS)
Table 6 describes Continuous Access XP split types. You can split a Continuous Access XP pair at any time
after the initial copy operation is complete. You must split a Continuous Access XP pair to perform media
maintenance on the P-VOL or change the S-VOL (S-VOL write enable).
When you split a Continuous Access XP Synchronous pair, the MCU ensures synchronization by
completing any pending update copy operation before changing the status to PSUS. After the pair status
changes to PSUS, 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 and pairsplit-r options. If
the P-VOL accepts write operations while the pair is split, the MCU tracks P-VOL cylinders updated. If you
enabled the S-VOL write option when you split the pair, the RCU tracks S-VOL cylinders updated while the
pair is split. When the pair is resumed (pairresync), 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.
When you split a Continuous Access XP Asynchronous pair, the MCU and RCU ensure synchronization by
completing or discarding pending update copy operations according to the user-specified drain/purge
pairsplit option. The MCU and RCU track recordsets discarded during the pairsplit operation. After the
pair status changes to PSUS, the MCU stops performing recordset operations for the pair, continues
accepting write I/Os for the split Continuous Access XP Async P-VOL, and tracks P-VOL cylinders updated
while the pair is split. If you enabled the S-VOL write option when you split the pair, the RCU also tracks
the S-VOL cylinders updated while the pair is split. When the 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.
A split (or suspended) Continuous Access XP Async S-VOL has an additional status called consistency
status. The 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.
Pair Status for Continuous Access XP Asynchronous only:
Suspending Pair is not synchronized. This pair is transitioning
from PAIR or COPY to PSUS/PSUE. When the
split/suspend pair operation is requested, the
status of all affected pairs changes to Suspending.
When the split/suspend operation is complete, the
status changes to PSUS/PSUE.
Read/write Read only
Deleting Pair is not synchronized. This pair is transitioning
from PAIR, COPY, or PSUS/PSUE to SMPL. When
the pairsplit-S operation is requested, the status of
all affected pairs changes to Deleting. When the
pairsplit-S operation is complete, the status
changes to SMPL.
Read/write Read only
Table 5 Continuous Access XP Asynchronous pair status descriptions (continued)
Pair status Description P-VOL access S-VOL access
Table 6 Continuous Access XP split types (PSUS)
Type Applies to Description
PSUS,
P-VOL by Operator
P-VOL
(
Continuous Access
XP Sync only)
You split the pair from the MCU using the P-VOL Failure option.
S-VOL split type is PSUS-by MCU.
PSUS,
S-VOL by Operator
P-VOL, S-VOL You split the pair from the MCU or RCU using the S-VOL option.
PSUS,
by MCU
S-VOL The RCU received a request from the MCU to split the pair. P-VOL
split type is PSUS-P-VOL by Operator or PSUS-S-VOL by Operator.
PSUS,
Delete pair to RCU
P-VOL The MCU detected the S-VOL status changed to SMPL because you
deleted the pair (pairsplit-S) from the RCU. The pair cannot be
resumed because the S-VOL does not have the PSUS/PSUE status.