HP StorageWorks Data Replication Manager HSG80 ACS Version 8.7P Configuration Guide (AA-RPHZF-TE, March 2004)

Remote Copy Set Features
40 Data Replication Manager HSG80 ACS Version 8.7P Configuration Guide
Write History Log Unit Restrictions
Things to remember about write history log units include:
■ Up to 12 write history log units can be assigned (12 possible remote copy sets).
■ There can be only one write history log unit assigned to an association set.
— No new remote copy sets can be added to an association set while write history
logging is active.
— No new target can be added to a remote copy set that is part of an association set while
write history logging is active.
■ The write history log unit must be a mirrorset or a striped mirrorset.
■ Host access must be disabled to create a write history log unit.
■ Write-back caching must be disabled to create a write history log unit.
■ Other unit settings must be the default settings to create a write history log unit.
■ The write history log unit must reside at the current initiator site.
■ Upon site failover, the write history log unit and association set must be reconfigured.
■ The write history log unit cannot be a partitioned unit.
■ The write history log unit must be a fixed size.
Reaching the End of a Write History Log Unit
Upon reaching the end of the write history log unit:
■ The write history log unit is not wrapped and processing does not start over at the
beginning. The write history log unit only resets to the beginning when it is empty.
■ All active targets engaged in logging or mini-merging will require a full copy when the
link is restored or when the RESUME command is issued.
■ A full copy will occur when the target members are not removed from the remote copy
sets.
■ You can display a write history log unit utilization with SHOW REMOTE and VTDPY
DISPLAY REMOTE commands.
The time required to reach the end of a write history log unit depends on several factors:
■ Size of the write history log unit
■ How long the link is down
■ How long a target backup takes
■ Host write workload
■ Number of remote copy sets actively logging to the same unit