Compaq StorageWorks Data Replication Manager HSG80 ACS Version 8.5P Operations Guide

64 Compaq StorageWorks Data Replication Manager HSG80 ACS Version 8.5P Operations Guide
If a remote copy set target member fails, a write issued to that remote copy set will
cause a write failure at the target. The target member will be removed, and the remote
copy set will be put in failsafe lock condition. If you wish to continue operation at the
initiator site, be sure to change the remote copy set error mode to normal before
proceeding.
If a remote copy set member at the initiator fails, the unit will become unavailable to
the host. The target member of the remote copy set is not read and write accessible
through the initiator controller. Recovery from this condition requires a failover to the
target site.
Remote Copy Set Worldwide LUN ID
Remote copy sets are assigned a unique worldwide LUN ID (WWLID) that represents
their specific LUN. The controller identifies a remote copy set by its WWLID and
presents it to the target when a failover is executed for that unit. If the remote copy set is
failed over to a target site, its WWLID will be transferred with that unit, even though it
may not be consistent with the controllers worldwide ID or the IDs of the other units
presented on the new controller. The remote copy set will not assume a new WWLID,
regardless of those that appear at the target site.
Write History Logging
Once write history logging commences to a log unit, care must be taken when choosing to
disable logging. Issuing the SET AssociationSetName NOLOG_UNIT command may
incur a full copy operation on the remote copy set. For example, the controller is logging
updates for a remote copy set because the links to the target are down. If the log unit is
disabled during this time, the controller cannot use the write history log to update the
target when the links are restored as some operations were not written to the log.
Therefore, a full copy is initiated. Also, the log disk is no longer known to the controller.