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

36 Overview of Continuous Access XP Journal
is suspended. Primary and secondary arrays also keep track of any journal data discarded during the
pair suspension. When the suspended Continuous Access XP Journal pair is resumed (pairresync), the
secondary array sends the secondary data volume’s bitmap to the primary array, and the primary array
merges the primary and secondary data volumes’ bitmaps to determine which cylinders/tracks are
out-of-sync. The primary array merges the primary and secondary data volumes’ bitmaps to identify
out-of-sync cylinders/tracks. This method ensures that all cylinders/tracks containing journal data
discarded at the secondary array are resynchronized at this time.
A split (or suspended) Continuous Access XP Journal secondary data volume has an additional status
called the consistency status. The consistency status is displayed only at the secondary array and indicates
the update sequence consistency of the secondary data volume with respect to the other secondary data
volume in the same group. Table 6 describes consistency statuses for split or suspended Continuous
Access XP Journal secondary data volumes (the consistency status is displayed only at the secondary
array).
Continuous Access XP Journal suspension conditions
Continuous Access XP Journal operations involve additional suspension conditions related to
asynchronous journal operations. The primary and secondary arrays can detect Continuous Access XP
Journal suspension conditions and suspend Continuous Access XP Journal pairs. The primary array stores
a differential bitmap per Continuous Access XP Journal primary data volume in shared memory. The
secondary array stores a differential bitmap per Continuous Access XP Journal secondary data volume in
shared memory. When a Continuous Access XP Journal pair is suspended, tracks containing the following
journal are marked in the differential bitmap as modified (to be copied during the pairresync operation):
• Journal data the primary array has created, but has not sent to the secondary array yet
After marking these primary data volume tracks as modified, the primary array discards the journal
data.
• Journal data that has been sent to the secondary array, but has not been acknowledged by the
secondary array
After marking these primary data volume tracks as modified, the primary array discards the journal
data. This ensures that journal data lost during transmission to the secondary array is identified and
marked.
• Journal data that has reached the secondary array, but has not been restored yet
After marking these primary data volume tracks as modified, the primary array discards the journal
data. Therefore, the secondary array can check and mark journal data that has not been restored.
The primary array does not discard journal data from the master journal volume until the primary
array receives the restored journal volumes’ sequence numbers, which are included in read journal
commands from the secondary array.
Table 7 Suspend types (PSUE)
Type Applies to Description
PSUE, S-VOL Failure Primary data volume,
Secondary data volume
The primary array detected an error during
secondary array communications or during update
copy. In this case, the secondary data volume
suspend type is usually PSUE-S-VOL Failure.
PSUE, MCU IMPL Primary data volume,
Secondary data volume
The primary array could not find valid control
information in its nonvolatile memory during IMPL.
This condition occurs only if the primary array is
without power for more than 48 hours (for example,
a power failure and fully discharged backup
batteries).
PSUE Initial Copy Failed Primary data volume,
Secondary data volume
The Continuous Access XP Journal pair was
suspended before the initial copy operation
completed. Data on the secondary data volume is not
identical to data on the primary data volume.
PSUE, MCU P/S OFF
Secondary data volume The primary array is powered off.