HP StorageWorks XP Remote Web Console Software - Manual (Page 36)

If a TrueCopy for Mainframe 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.
When a TrueCopy for Mainframe pair is suspended, the MCU stops performing update copy
operations to the R-VOL. For a suspended TrueCopy for Mainframe 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 records the data in the M-VOL tracks that are updated while the pair is suspended as
the differential data. For a suspended TrueCopy for Mainframe Asynchronous 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 records the data in the M-VOL tracks that are updated
while the pair is suspended as the differential data.
A suspended TrueCopy for Mainframe Asynchronous R-VOL has an additional status called the
consistency status which is displayed only at the RCU. The consistency status of a suspended
TrueCopy for Mainframe Asynchronous R-VOL indicates its update sequence consistency with
respect to the other R-VOLs in the same group.
“Consistency Status for Suspended TrueCopy for
Mainframe Async P-Vols” (page 37) lists and describes the consistency status descriptions for
suspended TrueCopy for Mainframe Asynchronous R-VOLs.
When a TrueCopy for Mainframe 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 which indicates the reason for suspension.
If you need write access to an R-VOL, you must release the pair.
Table 9 Suspend Types
Description Applies to Suspend Type
The user suspended the pair from the
MCU using the M-VOL Failure option.
The R-VOL suspend type is by MCU. M-VOL (TrueCopy for Mainframe Sync
only) M-VOL by operator
The user suspended the pair from the
MCU or RCU using the R-VOL option. M-VOL, R-VOL R-VOL by operator
The RCU received a request from the
MCU to suspend the pair. The M-VOL R-VOL by MCU
suspend type is M-VOL by Operator or
R-VOL by Operator.
The MCU detected an error condition
at the RCU which caused the MCU to M-VOL by RCU
suspend the TrueCopy for Mainframe
pair. The R-VOL suspend type is by
MCU.
The MCU detected that the R-VOL status
changed to simplex because the user M-VOL Release Pair to RCU
released the pair from the RCU. The
pair cannot be resynchronized because
the R-VOL does not have the suspended
status.
The MCU detected an error during
communication with the RCU or an I/O M-VOL R-VOL Failure
error during update copy. In this case,
the R-VOL suspend type is usually by
MCU.
The MCU could not find valid control
information in its nonvolatile memory M-VOL, R-VOL MCU IMPL
during the IMPL procedure. This
36 About TrueCopy for Mainframe Operations