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

Resync for Swapping operation will be performed (after the copy process).
The Swap operation is required to copy Nontransmitted P-VOL data within a
given timeout value (specified by the -t <timeout> option).

SVOL-takeover function

The function makes it so the takeover node alone can use the secondary
volume (except in COPY state) in SSUS(PSUS) state (i.e., reading and writing
are enabled), on the assumption that the remote node (possessing the
primary volume) cannot be used.
The data consistency of the secondary volume is judged by its status and
fence level. If this check proves that data is not consistent, the SVOL-
takeover function fails. If this check proves that data is consistent then this
function will try to switch the S-VOL to a primary volume using a Resync for
Swapping, and if it succeeds then this function will return Swap-takeover,
else this function will return SVOL-SSUS-takeover as the return value of
horctakeover command. In case of a Host failure, this function will be
returned as Swap-takeover. In case of a FICON or P-VOL site failure, this
function will be returned as SVOL-SSUS-takeover. A SVOL-takeover can be
specified by the granularity of a paired logical volume, consistency group, or
volume group. If a SVOL-takeover is specified for a volume group, a data
consistency check is executed for all volumes in the group. Inconsistent
volumes are picked out and displayed in the execution log file as shown
below:
Example:
Group Pair vol Port targ# lun# LDEV#...Volstat Status Fence To be...
oradb1 ora001 CL1-A 1 5 145...S-VOL PAIR NEVER Analyzed
oradb1 ora002 CL1-A 1 6 146...S-VOL PSUS STATUS Suspected
Even so, the SVOL-takeover function enables the secondary volume to be
used (i.e., reading and writing are enabled) since it assumes that the remote
node (possessing the primary volume) cannot be used.
TrueCopy Async/Universal Replicator specific behavior for SVOL-
takeover: The S-VOL side CCI will issue a Suspend for Swapping to the S-
VOL side storage system. Non-transmitted P-VOL data will be copied to the S-
VOL and a Resync for Swapping operation will be performed (after the copy
process).
In case of a Host failure, this data synchronize operation will be accomplished
and the SVOL-takeover function will return as Swaptakeover after attempting
a Resync for Swapping.
In case of a FICON or P-VOL site failure, this data synchronization operation
might fail. Even so, the SVOL-takeover function will do Suspend for
Swapping, and enable the secondary volume to be used.
As a result, this function will return as SVOL-SSUS-takeover. Through this
behavior, you will be able to judge that non-transmitted data of the primary
volume was not transmitted completely when a SVOL-takeover returns SVOL-
SSUS-takeover.
6-14
Data replication operations with CCI
Command Control Interface User and Reference Guide