Learn how to make application programs resilient.
A resilient application is expected to have the following characteristics:
- The application can be restarted on this node or another node
- The application is accessible to the client through the IP address
- The application is stateless or state information is known
- Data that is associated with the application is available after switchover
The three essential elements that make an application resilient
to system outages in a clustered environment are:
- The application itself
- How tolerant is the application to errors or to system outages, and how
transparently can the application restart itself?
The application can handle this through the use of clustering capabilities.
- Associated data
- When an outage occurs, does it affect the availability of any associated
data?
A cluster middleware IBM Business Partner replication product which takes advantage of the clustering capabilities can handle this. Alternatively, the data can be stored in a switchable independent disk pool (switchable independent ASP).
- Control capabilities and administration
- How easy is it to define the environment that supports the availability
of the data and the application? A third-party cluster management
solution that uses the clustering APIs and also combines resilient applications
with resilient data can handle this.