Swap-Takeover Function - Hitachi VSP F1500 User And Reference Manual

Nop-takeover: No operation is done to allow local writes, though the
takeover command is accepted. Personality swaps must be accomplished in
another way.
Unconformable: A pair of volumes are not conformable to each other as a
pair (that is, one P-VOL, one S-VOL). The takeover command execution
terminates abnormally.
Reject: The takeover command is rejected, and the operation terminates
abnormally.
Unknown: The attribute of the remote node is unknown and cannot be
identified. This means that the remote node system has gone down or cannot
communicate over the LAN.
SSWS: Since the SSWS state is referring to a Suspend for Swapping with S-
VOL Side only, the SSWS state is displayed as SSUS (SVOL_PSUS) by all
commands except the -fc option of the pairdisplay command.

Swap-takeover function

The P-VOL status at the remote node is PAIR or PFUL (TrueCopy Async and
over high-water mark) and the S-VOL has mirroring consistency. In such a
state, it is possible to swap the primary and secondary volume designations
to continue operation. The takeover command internally executes the
operating commands (explained later) step by step, to swap the primary and
secondary volume designations. Swapping can be specified at the granularity
of volume pair, consistency group, or volume group.
The swap-takeover function does not use Simplex and No Copy mode for
Swapping in order to guarantee mirror consistence more surely, and it is
included as a function of SVOL-takeover.
1 As the preliminary step of swap-takeover, the command orders a
.
Suspend for Swapping (SSWS) for the local volume (S-VOL). If this step
fails, the swap-takeover function is disabled and it will be returned at an
error.
2 The command orders a Resync for Swapping for switch to the primary
.
volume that the local volume (S-VOL) is swapped as the NEW_PVOL and
re-synchronizes the NEW_SVOL based on the NEW_PVOL. As for the
number of simultaneous copy tracks, if the remote host is known then the
command will use the value of P-VOL specified at paircreate time, else
(remote host is Unknown) the command will use a default of 3 as the
number of tracks for Resync for Swapping.
If this step fails, the swap-takeover function will be returned at SVOL-
SSUS-takeover, and the local volume (S-VOL) is maintained in
SSUS(PSUS) state which permits WRITE and maintaining delta data
(BITMAP) for the secondary volume. Also this special state is displayed as
SSWS state using -fc option of pairdisplay command.
TrueCopy Async/Universal Replicator specific behavior for swap-
takeover: The S-VOL side CCI will issue a Suspend for Swapping to the S-
VOL side storage system. Non-transmitted data which remains in the FIFO
queue (sidefile) of the primary volume will be copied to the S-VOL side and a
Data replication operations with CCI
Command Control Interface User and Reference Guide
6-13