Hitachi AMS 2000 Series, Reference Manual

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Performing CCI Operations
1–49
Hitachi AMS 2000 Family Command Control Interface (CCI) Reference Guide
PVOL-takeover function (TrueCopy only)
The PVOL-takeover function releases the pair state as a group, since that
maintains the consistency of the secondary volume at having accepted
horctakeover command when the primary volume is fenced (“data” and
“PSUE” state, “PSUE” volume are contained in the group). This function
allows the takeover node to use the primary volume (that is, reading and
writing are enabled), on the assumption that the remote node (possessing
the secondary volume) cannot be used. PVOL-takeover can be specified for
a paired volume or a group.
The PVOL-takeover function executes the following two commands:
• PVOL-PSUE-takeover: Changes the primary volume to the suspend
(PSUE, PSUS) state which enables write I/Os to all primary volumes of
the group. The action of the PVOL-PSUE-Takeover causes PSUE, PSUS,
or both PSUE and PSUS to be intermingled in the group. This
intermingled pair status is PSUE as the group status; therefore,
pairvolchk command returned gives priority to PSUE rather than PSUS
as the group status. This special state turns back to the original state
when the pairresync command is issued.
• PVOL-SMPL-takeover: Changes the primary volume to the simplex
(SMPL) state. First, PVOL-takeover executes PVOL-PSUE-takeover
further than PVOL-SMPL-takeover. If the PVOL-PSUE-takeover function
fails, the PVOL-SMPL-takeover function is executed.
Applications of the horctakeover command
The basic TrueCopy or TCE commands (takeover, pair creation, pair
splitting, pair resynchronization, event waiting) can be combined to enable
recovery from a disaster, backup of paired volumes, and many other
operations (that is, restoration of paired volumes based on the secondary
volume, swapping of the paired volumes). Figure 1-36 illustrates the flow of
starting operations on a UNIX server at the secondary site using the
TrueCopy or TCE horctakeover command.
Figure 1-37 illustrates the flow of starting operations on a Windows 2000 or
Windows Server server at the secondary site using the TrueCopy or TCE
horctakeover command.