BEST_POSSIBLE_RETENTION Function

192.1.1 BEST_POSSIBLE_RETENTION Function

This function returns the best possible value for the undo_retention parameter that the current undo tablespace can satisfy in order to maximize the usage for the current undo tablespace based on the historical information of a given period.

Syntax

Viewing the output using the historical information in memory:

DBMS_UNDO_ADV.BEST_POSSIBLE_RETENTION()
RETURN NUMBER;

Viewing the output using start time and end time:

DBMS_UNDO_ADV.BEST_POSSIBLE_RETENTION(
    start_time IN DATE,
    end_time   IN DATE)
RETURN NUMBER;

Viewing the output using begin and end AWR snapshot ID:

DBMS_UNDO_ADV.BEST_POSSIBLE_RETENTION(
    begin_snap IN NUMBER,
    end_snap   IN NUMBER)
RETURN NUMBER;

Parameters

Table 192-2 BEST_POSSIBLE_RETENTION Function Parameters

Parameter	Description
`start_time`	Start time of the given period.
`end_time`	End time of the given period.
`begin_snap`	Begin snapshot identifier. It is based on historical information in AWR from the `begin_snap` identifier.
`end_snap`	End snapshot identifier. It is based on historical information in AWR until the `end_snap` identifier.