Oracle Database automatically
maintains a system-defined moving window baseline. The default window size for
the system-defined moving window baseline is the current AWR retention period,
which by default is eight days.
If you are planning to use adaptive thresholds, consider using a larger moving window (such as 30 days) to accurately compute threshold values. You can resize the moving window baseline by changing the number of days in the moving window to a value that is equal to or less than the number of days in the AWR retention period. Therefore, to increase the size of a moving window, you first need to increase the AWR retention period accordingly.
The AWR retention period and window size for the system-defined moving window baseline are two separate parameters. The AWR retention period must be greater than or equal to the window size for the system-defined moving window baseline.
If you are planning to use adaptive thresholds, consider using a larger moving window (such as 30 days) to accurately compute threshold values. You can resize the moving window baseline by changing the number of days in the moving window to a value that is equal to or less than the number of days in the AWR retention period. Therefore, to increase the size of a moving window, you first need to increase the AWR retention period accordingly.
The AWR retention period and window size for the system-defined moving window baseline are two separate parameters. The AWR retention period must be greater than or equal to the window size for the system-defined moving window baseline.
This system-defined baseline
provides a default baseline for EM performance screens to compare the
performance with the current database performance.
Note: The default retention period for snapshot data has been changed from
seven days to eight days in Oracle Database 11g to ensure the capture of
an entire week of performance data.
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