UR PSUS types and behaviors

The PSUS status, which indicates that a pair is split or suspended, can be set by the user or by the system from the primary or secondary storage system. The following table lists and describes the PSUS status types.

PSUS type

Applies to

Description

S-VOL by Operator

P-VOL, S-VOL

  • The user split the pair from the primary or secondary storage system using the S-VOL-write option.
  • CCI displays this PSUS type as SSWS.

By MCU

S-VOL

  • The secondary storage system received a request from the primary storage system to split the pair.
  • The P-VOL PSUS type is S-VOL by Operator.
  • CCI displays this PSUS type as SSWS.

By RCU

P-VOL, S-VOL

  • The primary storage system suspended the pair after detecting an error condition on the secondary storage system.
  • The S-VOL suspend type is S-VOL Failure.
  • CCI displays this suspend type as PSUE.

Pairsplit-S to RCU

P-VOL

  • The primary storage system detected that the S-VOL is unpaired after the user released the pair from the secondary storage system.
  • The pair cannot be resynchronized.

JNL Cache Overflow

P-VOL, S-VOL

  • The pair was suspended because the journal volume was near capacity.
  • CCI displays this PSUS type as SSWS.
  • A pair can be split after the initial copy is complete.
  • A pair must be split to perform maintenance on the P-VOL, or to enable write-access to the S-VOL.
  • After the status changes to PSUS, the primary storage system performs the following tasks:
    • Stops journal-obtain operations
    • Continues to accept write I/Os from hosts to the P-VOL
    • Keeps track of the updated P-VOL tracks
  • When the UR pair is split by the user, the primary storage system and secondary storage system will either execute suspended update copy, synchronize the pair then split or delete suspended update copy then split the pair based on the user specified Split Mode option (Flush or Purge). The journal data that is deleted during UR pair split is stored in the primary and secondary storage systems. When the pair status becomes PSUS, the primary storage system will stop obtaining the journal for the pair and accept write I/O for split UR P-VOL and record the updated P-VOL track during pair split.
  • If you enable the S-VOL write option (Secondary Volume Write) when splitting the pair, the secondary storage system keeps track of updated S-VOL tracks. When the pair is resynchronized, the secondary storage system sends the S-VOL track bitmap to the primary storage system, which then merges P-VOL and S-VOL bitmaps to synchronize the tracks.
  • A split or suspended S-VOL has a separate consistency status, which indicates the S-VOL’s update sequence consistency with respect to the other S-VOLs in the associated journal. The consistency status is displayed only on the secondary storage system. The following table lists and describes the S-VOL consistency statuses.
Table 1: S-VOL consistency statuses

Consistency status

Description

Volume

  • Only the current pair was split or suspended.
  • Update sequence consistency between this S-VOL and other S-VOLs in the associated journal is not ensured.
  • This S-VOL cannot be used for disaster recovery at the secondary site.
  • This status is indicated when:
    • The pair is split by the user using the Split Pairs window (Suspend Range-Volume (LU) pairsplit option).
    • The pair is suspended due to a failure that did not affect the entire journal.

Mirror

  • The pair was split or suspended along with the other pairs in the associated mirror.
  • Update sequence consistency between this S-VOL and other S-VOLs in this mirror is ensured.
  • This S-VOL can be used for disaster recovery on the secondary storage system.
  • This status is indicated when:
    • The mirror is split using the Split Mirrors window (or by specifying mirror of the CCI pairsplit -r option).
    • All pairs in the associated mirror are suspended due to a failure that affected the entire group, for example, path failure.
    • One pair in the mirror was suspended due to a failure that did not affect the entire group.
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