Performance.Impact.on.Availability
Downtime is not the only concern when dealing with high availability. Most large applications
encounter diverse processing needs. On one hand, the online users require good response
time from many short transactions. On the other hand, large batch jobs (e.g., reports and
complex extracts) expect high throughput of a handful of very large transactions. These con-
flicting needs cause response time to fluctuate, decreasing the reliability and availability of
the application. This is especially a concern with applications that provide services directly
to end users and consumers such as in e-commerce applications.
Redundancy.is.the.Key.to.Availability
The logical solution for increased availability is to maintain the data in more than one place.
Coincidentally, one of the best solutions for improving the application response time is to
separate the batch reporting and extract processing from the Online Transaction Processing
(OLTP). This solution also requires a redundant database. This means that owners of large
critical applications are seeking a solution that provides both high availability and the ability
to offload non-critical processing from the main system (Aronoff, 2003).
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