186.1.4 REQUIRED_RETENTION Function

This function returns the required value for the undo_retention parameter to satisfy the longest query based on undo statistics available for a given period.

Syntax

Viewing the output using the historical information in memory:

DBMS_UNDO_ADV.REQUIRED_RETENTION()
RETURN NUMBER;  

Viewing the output using start time and end time:

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

Viewing the output using begin and end AWR snapshot ID:

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

Parameters

Table 186-5 REQUIRED_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.