V$FILE_HISTOGRAM

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

CON_ID

NUMBER

The ID of the container to which the data pertains. Possible values include:

  • 0: This value is used for rows containing data that pertain to the entire CDB. This value is also used for rows in non-CDBs.

  • 1: This value is used for rows containing data that pertain to only the root

  • n: Where n is the applicable container ID for the rows containing data