Then again, I believe there??™s no such thing as a technical
cure-all. Mirroring is extremely useful, but make sure you consider the possible
ramifications of any given use.
CHAPTER 8 n DATABASE MIRRORING 223
When discussing availability, you need to be clear about whether you??™re referring to
availability as physical, measurable downtime or the perception of downtime. Often, too
much focus is placed on measurable downtime (with good reason??”it??™s easily quantifiable)
at the expense of the user experience. If I??™m the user of an application, it doesn??™t
matter to me if the back-end systems are really available. The only thing that matters to
me is whether I can continue to work. So what if the database is technically ???up???? If I can??™t
continue filling out my data-entry form (or if my work is lost), the system is unavailable
as far as I??™m concerned.
nNote User experience is also quantifiable in terms of uptime. It??™s often overlooked and downplayed
because it can be difficult to quantify. It takes time, cooperation, and coordination with end users, and
potentially some type of client-side coding, to capture timing data.
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