Hitachi TrueCopy for z/OS user guide (December 2005)

TrueCopy for z/OS user guide 39
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” on page 40.
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. Table 11 on page 40 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” on page 164.
NOTE: If you need write access to an R-VOL, you must delete the pair.
Table 10 Suspend types
Suspend Type Applies to Description
M-VOL by
operator
M-VOL
(TC390 Sync only)
The user suspended the pair from the MCU using the M-VOL Failure
option. The R-VOL suspend type is by MCU.
R-VOL by
operator
M-VOL, R-VOL The user suspended the pair from the MCU or RCU using the R-VOL
option.
by MCU R-VOL The RCU received a request from the MCU to suspend the volume pair.
The M-VOL suspend type is M-VOL by Operator or R-VOL by Operator.
by RCU M-VOL The MCU detected an error condition at the RCU that caused the MCU
to suspend the TC390 volume pair. The R-VOL suspend type is by MCU.
Delete Pair to
RCU
M-VOL The MCU detected that the R-VOL status changed to simplex because the
user deleted the pair from the RCU. The pair cannot be resumed
because the R-VOL does not have the suspended status.
R-VOL Failure M-VOL The MCU detected an error during communication with the RCU or an
I/O error during update copy. In this case, the R-VOL suspend type is
usually by MCU.
MCU IMPL M-VOL, R-VOL The MCU could not find valid control information in its nonvolatile
memory during the IMPL procedure. This condition occurs only if the
MCU is completely without power for more than 48 hours (for example,
power failure and fully discharged backup batteries).
Initial Copy
failed
M-VOL, R-VOL The volume pair was suspended before the initial copy operation was
complete. The data on the R-VOL is not identical to the data on the
M-VOL.
by FREEZE M-VOL, R-VOL
(TC390 Sync only)
The volume pair was suspended by the CGROUP/RUN TSO command.
See ”CGROUP (FREEZE/RUN) Support” on page 158.