Managing Serviceguard 13th Edition, February 2007

Designing Highly Available Cluster Applications
Minimizing Planned Downtime
Appendix C412
Providing Online Application Reconfiguration
Most applications have some sort of configuration information that is
read when the application is started. If to make a change to the
configuration, the application must be halted and a new configuration
file read, downtime is incurred.
To avoid this downtime use configuration tools that interact with an
application and make dynamic changes online. The ideal solution is to
have a configuration tool which interacts with the application. Changes
are made online with little or no interruption to the end-user. This tool
must be able to do everything online, such as expanding the size of the
data, adding new users to the system, adding new users to the
application, etc. Every task that an administrator needs to do to the
application system can be made available online.
Documenting Maintenance Operations
Standard procedures are important. An application designer should
make every effort to make tasks common for both the highly available
environment and the normal environment. If an administrator is
accustomed to bringing down the entire system after a failure, he or she
will continue to do so even if the application has been redesigned to
handle a single failure. It is important that application documentation
discuss alternatives with regards to high availability for typical
maintenance operations.