Resynchronizing Pairs (Pairresync) - Hitachi TAGMASTORE MK-90RD011-25 User Manual

4.4

Resynchronizing Pairs (Pairresync)

The pairresync command re-establishes a split pair and then restarts the update copy
operations to the secondary volume (see Figure 4.5). The pairresync command can
resynchronize either a paired logical volume or a group of paired volumes. The normal
direction of resynchronization is from the primary volume to the secondary volume. If the -
-restore option is specified (ShadowImage only), the pair is resynchronized in the reverse
direction (i.e., secondary volume to primary volume). Figure 4.6 shows the normal and
restore resync operations. The primary volume remains accessible during pairresync, except
when the -restore option is specified. The secondary volume becomes write-disabled when
the pairresync command is issued. Table 4.7 lists and describes the pairresync command
parameters and returned values. The primary volume's server is automatically detected by
the pairresync command, so the server does not need to be specified in the pairresync
command parameters. Table 4.8 lists the error codes for pairresync.
Pairresync terminates before resynchronization of the secondary (or primary) volume is
complete. Use the pair event waiting or pair display command to verify that the resync
operation completed successfully (status changes from COPY to PAIR). The execution log file
also shows completion of the resync operation. The status transition of the paired volume is
judged by the status of the primary volume. The fence level is not changed (only for
TrueCopy, TrueCopy Async, or UR).
If no data was written to the secondary volume while the pair was split, the differential data
on the primary volume is copied. If data was written to the secondary volume, the
differential data on the primary volume and secondary volume is copied. This process is
reversed when the ShadowImage -restore option is specified.
Before issuing the pairresync command (normal or reverse direction), make sure that the
secondary volume is not mounted on any UNIX system. Before issuing a reverse pairresync
command, make sure that the primary volume is not mounted on any UNIX system.
Note on Quick Resync/Restore: If the "$HORCC_RSYN=QUICK" /"$HORCC_REST=QUICK"
environment variable is set (USP V/VM or USP/NSC), the "pairresync" operation will be
performed as Quick Resync regardless of the system option mode 87/80 setting via SVP. The
$HORCC_RSYN and $HORCC_REST environment variables are ignored by 9900V/9900.
Hitachi TrueCopy only: The swaps(p) option is used to swap volume from the SVOL(PVOL)
to PVOL(SVOL) at suspending state on the SVOL(PVOL) side, and resynchronize the
NEW_SVOL based on the NEW_PVOL. At the result of this operation, the volume attributes of
own host (local host) become the attributes for the NEW_PVOL(SVOL). The paircreate
command cannot execute copy rejection in case of an error condition which made the target
volume is accompanied by maintenance work. The swaps(p) option will:
Ignore the -l option.
Use a default of three for number of copy tracks (-c size) when -c size option is
omitted.
Execute at PAIR state as well as PSUS/PSUE state (not applicable to COPY and SMPL).
Since the target volume of the local host has been already the PVOL(SVOL), this target
volume is skipped an operation.
180 Chapter 4 Performing CCI Operations