REQUIRED_UNDO_SIZE Function

187.1.5 REQUIRED_UNDO_SIZE Function

This function returns the required undo tablespace size (in MB) to satisfy certain undo retention value based on undo statistics available for a given period.

Syntax

Note:

Zero will be returned if the information about the given period is not available.

Viewing the output using the historical information in memory:

DBMS_UNDO_ADV.REQUIRED_UNDO_SIZE(
    retention IN NUMBER)
RETURN NUMBER;

Viewing the output using start time and end time:

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

Viewing the output using begin and end AWR snapshot ID:

DBMS_UNDO_ADV.REQUIRED_UNDO_SIZE(
    retention  IN NUMBER,
    begin_snap IN NUMBER,
    end_snap   IN NUMBER)
RETURN NUMBER;

Parameters

Table 187-6 REQUIRED_UNDO_SIZE Function Parameters

Parameter	Description
`retention`	Retention value you want to set for the `undo_retention` `init.ora` parameter.
`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.