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Oracle® Database Reference
12c Release 1 (12.1)

E17615-23
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V$DB_CACHE_ADVICE

V$DB_CACHE_ADVICE contains rows that predict the number of physical reads for the cache size corresponding to each row. The rows also compute a "physical read factor," which is the ratio of the number of estimated reads to the number of reads actually performed by the real buffer cache during the measurement interval.

Column Datatype Description
ID NUMBER Buffer pool identifier (ranges from 1 to 8)
NAME VARCHAR2(20) Buffer pool name
BLOCK_SIZE NUMBER Block size in bytes for buffers in this pool. Possible values: the standard block size, the power of 2 nonstandard block sizes, 2048, 4096, 8192, 16384, 32768.
ADVICE_STATUS VARCHAR2(3) Status of the advisory. ON indicates it is currently running; OFF indicates it is disabled (in this case the estimates are historical and calculated when last enabled).
SIZE_FOR_ESTIMATE NUMBER Cache size for prediction (in megabytes)
SIZE_FACTOR NUMBER Size factor with respect to the current cache size
BUFFERS_FOR_ESTIMATE NUMBER Cache size for prediction (in terms of buffers)
ESTD_PHYSICAL_READ_FACTOR NUMBER Physical read factor for this cache size, which is the ratio of the number of estimated physical reads to the number of reads in the real cache. If there are no physical reads in the real cache, the value of this column is null.
ESTD_PHYSICAL_READS NUMBER Estimated number of physical reads for this cache size
ESTD_PHYSICAL_READ_TIME NUMBER Estimated disk read time
ESTD_PCT_OF_DB_TIME_FOR_READS NUMBER Estimated disk time as a percentage of the total time
ESTD_CLUSTER_READS NUMBER Estimated total number of blocks foreground processes read from the global cache (Real Application Clusters only)
ESTD_CLUSTER_READ_TIME NUMBER Estimated total amount of time, in seconds, foreground processes read from global cache (Real Application Clusters only)
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