Suspended pairs – HP StorageWorks XP Remote Web Console Software User Manual
Page 37
Hitachi TrueCopy for z/OS user guide
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Suspended pairs
on page 38 lists and describes the TC390 suspend types, which indicate the reason for
suspension. A user can suspend aTC390 pair at any time after the initial copy operation is complete. The
user must suspend a TC390 pair to perform ICKDSF maintenance on the M-VOL or to access the R-VOL
(read only mode). TC390 pairs are also suspended when the CGROUP/ RUN command is processed (see
” on page 173). When the user suspends a TC390 Synchronous pair,
the MCU ensures synchronization by completing any pending update copy operation before changing the
status to suspended. When the user suspends a TC390A pair, the MCU and RCU ensure synchronization
by either completing or discarding any pending update copy operations according to the user-specified
drain/purge suspend option.
A TC390 pair is suspended by the MCU when any of the following suspension conditions are detected. A
TC390A pair can also be suspended by the RCU (see ”
Suspended TrueCopy Asynchronous pairs
•
When the MCU detects that the user has deleted the volume pair from the RCU (for example, to access
an R-VOL at the remote site).
•
When the MCU detects an error condition related to the RCU, R-VOL, a TC390 Synchronous update
copy operation or a TC390A recordset operation (see ”
Suspended TrueCopy Asynchronous pairs
page 39).
•
When the RCU cannot execute DFW (DASD fast write) to the R-VOL (only if DFW required is selected).
•
When the MCU is unable to communicate with the RCU.
If a TC390 Synchronous update copy operation fails, the MCU maintains exact synchronization by
reporting a unit check and decommitting the M-VOL update so that the host system and application
program regard that write operation to the M-VOL as failed. For information on failed TC390A recordset
operations, see ”
Suspended TrueCopy Asynchronous pairs
When a TC390 pair is suspended, the MCU stops performing update copy operations to the R-VOL. For a
suspended TC390 Synchronous pair, the MCU may or may not continue accepting write I/Os for the
M-VOL depending on the M-VOL fence level and suspend option (if user-requested). If the MCU accepts
write I/Os for a suspended M-VOL, the MCU keeps track of the M-VOL cylinders that are updated while
the pair is suspended. For a suspended TC390A pair, the MCU and RCU keep track of any recordsets that
were discarded during suspension, and the MCU continues accepting write I/Os for the M-VOL and keeps
track of the M-VOL cylinders that are updated while the pair is suspended.
A suspended TC390A R-VOL has an additional status called the consistency status that is displayed only at
the RCU. The consistency status of a suspended TC390A R-VOL indicates its update sequence consistency
with respect to the other R-VOLs in the same group.
on page 39 lists and describes the
consistency status descriptions for suspended TC390A R-VOLs.
When a TC390 pair is suspended, whether user-requested or due to failure, the MCU generates sense
information to notify the host(s). If the host system supports IBM PPRC and the PPRC support RCU option is
enabled, this notification results in an IEA494I and/or IEA491E system console message that indicates the
reason for suspension. For more information on the IEA494I and IEA491E system console messages, see
IEA494I and IEA491E console messages
Deleting
This pair is not synchronized. This pair is in transition from duplex, pending duplex, or
suspended to simplex. When the delete pair operation is requested (by user), the status of
all affected pairs changes to deleting. When the delete pair operation is complete, the
status changes to simplex.
SEQCHK
The RCU encountered a non-time-stamped recordset for a TC390A pair using the System
timer type option. This status can be displayed at the MCU and RCU, but the MCU may not
have the most current information. Always use the pair status information displayed at the
RCU for disaster recovery.
Table 9
TrueCopy volume pair status (continued)
Pair Status
Description