Designing Disaster Tolerant High Availability Clusters, 10th Edition, March 2003 (B7660-90013)

Physical Data Replication for ContinentalClusters Using Continuous Access XP
Maintaining the Continuous Access XP Data Replication Environment
Chapter 6 323
Pairs must be manually recreated if both the primary and recovery XP
disk arrays are in the SMPL (simplex) state.
Make sure you periodically review the following files for messages,
warnings and recommended actions. You should particularly review
these files after system, data center and/or application failures:
• /var/adm/syslog/syslog.log
• /etc/cmcluster/<package-name>/<package-name>.log
• /etc/cmcluster/<bkpackage-name/<bkpackage-name>.log
Using the pairresync Command
The pairresync command can be used with special options after a failover
in which the recovery site has started the application and has processed
transaction data on the disk at the recovery site, but the disks on the
primary site are intact. After the CA link is fixed, you use the
pairresync command in one of the following two ways depending on
which site you are on:
• pairresync -swapp—from the primary site.
• pairresync -swaps—from the failover site.
These options take advantage of the fact that the recovery site maintains
a bit-map of the modified data sectors on the recovery array. Either
version of the command will swap the personalities of the volumes, with
the PVOL becoming the SVOL and SVOL becoming the PVOL. With the
personalities swapped, any data that has been written to the volume on
the failover site (now PVOL) are then copied back to the SVOL now
running on the primary site. During this time the package continues
running on the failover site. After resynchronization is complete, you can
halt the package on the failover site, and restart it on the primary site.
MetroCluster will then swap the personalities between the PVOL and
the SVOL, returning PVOL status to the primary site.
Some Further Points
• This toolkit may increase package startup time by 5 minutes or
more. Packages with many disk devices will take longer to start up
than those with fewer devices due to the time needed to get device
status from the XP disk array or to synchronize.