The PSUE status, which indicates that a pair is suspended, can be set only by the primary or secondary storage system. The primary storage system suspends a pair and changes its status to PSUE when it detects any of the following conditions:

• The user has released the pair on the secondary storage system.
• An error condition related to the S-VOL or an update copy operation.
• The primary storage system is not able to communicate with the secondary storage system.
• A Universal Replicator suspension condition is detected by the system.

The following table lists and describes the PSUE status types.

PSUE Type	Applies to	Description
S-VOL Failure	P-VOL, S-VOL	The primary storage system detected an error during communication with the secondary storage system or during update copying. S-VOL PSUE type is usually PSUE-S-VOL Failure. RAID Manager might display this status as SSWS.
MCU IMPL	P-VOL, S-VOL	The primary storage system could not find valid control information in its nonvolatile memory during IMPL (initial microprogram load). This condition occurs if the primary storage system is without power for more than 48 hours (power failure and fully discharged backup batteries).
Initial Copy Failed	P-VOL, S-VOL	The pair was suspended before the initial copy operation was complete. The data on the S-VOL is not identical to the data on the P-VOL. RAID Manager might display this status as SSWS.
MCU P/S OFF	S-VOL	The primary storage system is powered off. RAID Manager displays this as SSUS.

When a pair is suspended, the primary storage system stops performing journal-obtain operations for the pair. However, the primary storage system continues the following operations:

• Continues accepting write I/Os for the suspended P-VOL
• Keeps track of the P-VOL cylinders/tracks that are updated
• Keeps track of journal data discarded during the pair suspension. (Both primary and secondary storage systems do this.)

A split or suspended S-VOL has a separate consistency status that indicates its update sequence consistency with respect to the other S-VOLs in the associated journal. Consistency status displays on the secondary storage system only.

When the pair is resynchronized, the primary and secondary storage systems perform the following operations:

• The secondary storage system sends the S-VOL bitmap to the primary storage system
• The primary storage system merges the P-VOL and S-VOL bitmaps to synchronize the tracks

These actions ensure that all cylinders/tracks containing journal data discarded on the secondary storage system are resynchronized.