Comparative Performance Analysis with AWR Baselines
What is the proper threshold to set on
a performance metric? What is it that you want to detect? If you want to know
that the performance metric value indicates that the server is nearing
capacity, an absolute value is correct. But if you want to know that the
performance is different today than it was at this time last week, or last
month, the current performance must be compared to a baseline.
A baseline is a set of snapshots
taken over a period of time. These snapshots are grouped statistically to yield
a set of baseline values that vary over time. For example, the number of
transactions per second in a certain database varies depending on the time of the
day. The values for transactions per second are higher during working hours and
lower during nonworking hours. The baseline records this variation and can be
set to alert you if the current number of transactions per second is
significantly different from the baseline values.
Oracle Database 11g baselines provide the data
required to calculate time-varying thresholds based on the baseline data. The
baseline allows a real-time comparison of performance metrics with baseline
data and can be used to produce AWR reports that compare two periods.
What is the proper threshold to set on a performance metric?
What is it that you want to detect?
If you want to know that the performance metric value indicates that the server is nearing capacity, an absolute value is correct.
But if you want to know that the performance is different today than it was at this time last week, or last month, the current performance must be compared to a baseline.
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