Pair status definitions

(Unpaired- no HDvM - SN status)

SMPL

The volume is not assigned to a pair and is not in a journal.

Read/Write

Read/Write

COPY

COPY

The initial copy operation is in progress.

Read/Write

Read Only

PAIR

PAIR

The pair is synchronized. Updates to the P-VOL are duplicated on the S-VOL.

Read/Write

Read Only

HDvM - SN displays this status as PAIR

PFUL

If data in the journal volume exceeds the threshold (80 %), pair status changes to PFUL. The pair is not suspended; the copy operation continues.

If the journal option, Inflow Control, is set to Enable in HDvM - SN, or the modify journal command is executed in CCI when status changes to PFUL, host I/O is delayed because update I/O to the journal volume is delayed.

Read/Write

Read Only

PSUS

PSUS

SSUS

The pair has been split by the user and the P-VOL and S-VOL are no longer synchronized.

• The primary and secondary storage systems keep track of journal data discarded during the split operation.
• When the operation is performed on the primary storage system, the status of both the P-VOL and S-VOL changes to PSUS.
• When the operation is performed on the secondary storage system, the status of the S-VOL changes to PSUS, and the primary storage system detects this and changes the P-VOL status to PSUS.

SSUS is the S-VOL’s split status name.

See also UR PSUS types and behaviors.

Read/Write

Read Only, but if you enable the Secondary Volume Write option then split the pair from the primary site, it is Read/Write (Default is Disable).

PSUE

PSUE

The pair is suspended by the system due to an error; it is not synchronized.

• The primary and secondary storage systems keep track of journal data discarded during the suspension operation.
• The primary storage system keeps track of P-VOL tracks that are updated while the pair is suspended.
• When a UR suspension condition is detected, the primary storage system changes the P-VOL and S-VOL status to PSUE. If the secondary storage system detects the condition, it changes the S-VOL status to PSUE, and the primary storage system detects this and changes the P-VOL status to PSUE.

See also UR PSUS types and behaviors.

HDvM - SN: Read/Write CCI: Read/Write if no error in P-VOL

Read Only

Suspending

(No equivalent CCI status)

The pair is not synchronized and in transition from the PAIR or COPY status to PSUS or PSUE status.

Read/Write

Read Only

Deleting

(No equivalent CCI status)

The pair relationship is being deleted. When the operation is complete, the status changes to unpaired.

Read/Write

Read Only

HOLD

(No equivalent CCI status)

• When used with TC, this status indicates that the creation of a delta resync pair is completed. Delta resync might not be executed depending on the internal process status even if the creation of the delta resync pair is completed. When used with GAD, this status indicates that delta resync can be executed. If the P-VOL status is HOLD, the updated data of the TC or GAD S-VOL is stored in the master journal volume.
• Operations allowed:

  - Delta resync

  - Pair-delete

  - Change pair options

Read/Write¹

Read/Write²

HOLDING ³

(No equivalent CCI status)

When used with TC, this status indicates that the pair status is changing to HOLD so that the delta resync pair can be created.

Operations allowed on pairs in HOLDING status:

• Delta resync operation
• Pair release
• Change pair options

If the delta resync operation is run on a pair in HOLDING status, the operation could fail. If you specify Entire Copy for the Delta Resync Failure option (Change Journal Option dialog box), differential data is copied to an S-VOL.

When used with GAD, preparing for delta resync. Delta resync execution will fail if the pair status is HOLDING. Specification of Entire Copy is invalid for the Delta Resync Failure option. Resync the UR pair in case of delta resync failure.

Read/Write¹

-

HLDE

(No equivalent CCI status)

• An error occurred on a pair in HOLD status.
• When P-VOL status is HLDE, incoming write data for the TC or GAD S-VOL is not stored in the master journal volume.
• Operations allowed on pairs in HLDE status:

  - Recover pair status to standby (HOLD)

  - Pair delete

  - Change pair options

Read/Write¹

-

(No equivalent HDvM - SN status)

PFUS

This status results when the journal volume becomes full and suspends. Pair status changes from COPY, PAIR or PFUL to PFUS. The UR pair is suspended and the copy operation stops. Make sure to review configuration of the remote path and journal volume.

• If a Dynamic Provisioning virtual volume (DP-VOL) is used as the UR S-VOL, and the capacity of a pool-VOL is nearly full, UR status becomes PFUS and the pair is suspended.
• If the journal option Inflow Control is set to Yes when status changes to PFUS, the pair is not suspended for the time set in the Data Overflow Watch field in HDvM - SN, or for the time specified by the raidcom modify journal command with the -data_overflow_watch option in CCI, even when the journal volume becomes full. During the time it takes for the journal data area to clear, the response to host I/O is delayed.

  See Changing options used by journals for details about Data Overflow Watch.

Read /Write

Read Only, unless the write option is enabled.

(No equivalent HDvM - SN status)

SSWS

After Takeover, SSWS is the status of the S-VOL. With this status, data can be written to the S-VOL.

The copy flow between P-VOL and S-VOL is reversed by running the CCI horctakeover command or pairsplit -RS. Therefore, the S-VOL is ready for host write operations. During disaster recovery, the host can write data to the S-VOL in SSWS status at the intermediate site or secondary site. However, in a 3DC configuration in which three UR sites are combined, the host cannot write data to the S-VOL if the volume is shared by the mirror that includes the UR delta resync pair.

Read Only

Read/Write

Notes:

1. Access to the P-VOL depends on the status of the TC or GAD pair that shares the volume.
2. The UR S-VOL in HOLD status uses two mirrors. In a 3DC configuration combined with TrueCopy, accessing the S-VOL depends on the status of the mirror that is not HOLD. In a 3DC configuration in which three UR sites are combined, the host cannot write data to the S-VOL regardless of the mirror status.
3. HOLDING indicates either that differential data used for a delta resync operation does not exist or that the system cannot judge whether the delta resync can be performed without the differential data.

   When differential data does not exist in the secondary TC or GAD site, even after the S-VOL is updated, the differential data might be discarded due to the one of the following reasons:

   • The cache or shared memory was added to or removed from the system during maintenance work.
   • The system was powered off during maintenance work.
   • The UR or TCUR, TC, or GAD pair was suspended and then resynchronized.

   After the system is back to normal, differential data is stored again in the TC S-VOL if you update the data in the primary site.

   The delta resync operation can be executed without differential data if the primary site has not received a data update or if data in the TC or GAD S-VOL and the UR S-VOL is the same.

   Even if the delta resync operation without differential data is executable, the pair status changes to HOLD even when the differential data exists if the conditions for discarding the differential data are satisfied. To change the status of the pair to HOLD, update the data in the primary storage system after the recovery from the condition of the differential data discarding.

   If you cannot connect to the secondary site of TC or GAD due to failures or disasters, the transition from HOLDING to HOLD is not performed correctly. When used with GAD, keep updating I/O from the server to GAD P-VOL or S-VOL for about two minutes.