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 201-2 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.