V$FILE_HISTOGRAM

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V$FILE_HISTOGRAM displays a histogram of all synchronous single block reads on a per-file basis (for data files). The histogram has buckets of time intervals from < 1 ms, < 2 ms, < 4 ms, < 8 ms, ... < 2²¹ ms, < 2²² ms, and >= 2²² ms.

The histogram will not be filled unless the STATISTICS_LEVEL initialization parameter is set to ALL.

Column	Datatype	Description
FILE#	NUMBER	File number
SINGLEBLKRDTIM_MILLI	NUMBER	Amount of time the bucket represents (in milliseconds). If the duration = num, then this column represents waits of duration < num that are not included in any smaller bucket.
SINGLEBLKRDS	NUMBER	Number of waits of the duration belonging to the bucket of the histogram

Note:

The v$filestat view displays statistics per data file. This information can be skewed due to a couple of very large I/O waits, thus these waits might not be indicative of the system as a whole.

V$FILE_HISTOGRAM displays a histogram of all single block reads on a per-file basis. The histogram has buckets of time intervals from < 1 ms, < 2 ms, < 4 ms, < 8 ms, ... < 2^21 ms, < 2^22 ms, >= 2^22 ms. The histogram can be used to determine if the bottleneck is a regular or a unique problem. The frequency of each wait event versus the length of the wait events would be seen using the information in the v$file_histogram view.

Oracle data dictionary views

Oracle dynamic performance views

Last updated: 2009-12-22 Tuesday