Script - Check Current Undo Configuration and Advise Recommended Setup (Doc ID 1579035.1)

Script - Check Current Undo Configuration and Advise Recommended Setup (Doc ID 1579035.1)

APPLIES TO:

Oracle Database - Enterprise Edition - Version 8.1.7.0 and later
Information in this document applies to any platform.

GOAL

 This document is intended to check the current undo configuration and provides recommendation based on the previous workload.AUTION

  

This sample code is provided for diagnosis and troubleshooting purposes only, and is NOT supported by Oracle Support. It has been tested internally, however, we do not guarantee that it will work for you. Ensure that you run it in your test environment before using.

There are different scripts for database versions post 10g and prior to 10g. Ensure to execute the correct one to get the proper recommendation. Ensure to execute the script as SYS user.

SOLUTION

For database version 10g and above, use the following script. Ensure to execute the same as SYSDBA.

RDBMS version 10g and above:

SET SERVEROUTPUT ON
SET LINES 600
ALTER SESSION SET NLS_DATE_FORMAT = 'DD/MM/YYYY HH24:MI:SS';

DECLARE
    v_analyse_start_time    DATE := SYSDATE - 7;
    v_analyse_end_time      DATE := SYSDATE;
    v_cur_dt                DATE;
    v_undo_info_ret         BOOLEAN;
    v_cur_undo_mb           NUMBER;
    v_undo_tbs_name         VARCHAR2(100);
    v_undo_tbs_size         NUMBER;
    v_undo_autoext          BOOLEAN;
    v_undo_retention        NUMBER(5);
    v_undo_guarantee        BOOLEAN;
    v_instance_number       NUMBER;
    v_undo_advisor_advice   VARCHAR2(100);
    v_undo_health_ret       NUMBER;
    v_problem               VARCHAR2(1000);
    v_recommendation        VARCHAR2(1000);
    v_rationale             VARCHAR2(1000);
    v_retention             NUMBER;
    v_utbsize               NUMBER;
    v_best_retention        NUMBER;
    v_longest_query         NUMBER;
    v_required_retention    NUMBER;
BEGIN
    select sysdate into v_cur_dt from dual;
    DBMS_OUTPUT.PUT_LINE(CHR(9));
    DBMS_OUTPUT.PUT_LINE('- Undo Analysis started at : ' || v_cur_dt || ' -');
    DBMS_OUTPUT.PUT_LINE('--------------------------------------------------');

    v_undo_info_ret := DBMS_UNDO_ADV.UNDO_INFO(v_undo_tbs_name, v_undo_tbs_size, v_undo_autoext, v_undo_retention, v_undo_guarantee);
    select sum(bytes)/1024/1024 into v_cur_undo_mb from dba_data_files where tablespace_name = v_undo_tbs_name;

    DBMS_OUTPUT.PUT_LINE('NOTE:The following analysis is based upon the database workload during the period -');
    DBMS_OUTPUT.PUT_LINE('Begin Time : ' || v_analyse_start_time);
    DBMS_OUTPUT.PUT_LINE('End Time   : ' || v_analyse_end_time);
  
    DBMS_OUTPUT.PUT_LINE(CHR(9));
    DBMS_OUTPUT.PUT_LINE('Current Undo Configuration');
    DBMS_OUTPUT.PUT_LINE('--------------------------');
    DBMS_OUTPUT.PUT_LINE(RPAD('Current undo tablespace',55) || ' : ' || v_undo_tbs_name);
    DBMS_OUTPUT.PUT_LINE(RPAD('Current undo tablespace size (datafile size now) ',55) || ' : ' || v_cur_undo_mb || 'M');
    DBMS_OUTPUT.PUT_LINE(RPAD('Current undo tablespace size (consider autoextend) ',55) || ' : ' || v_undo_tbs_size || 'M');
    IF V_UNDO_AUTOEXT THEN
        DBMS_OUTPUT.PUT_LINE(RPAD('AUTOEXTEND for undo tablespace is',55) || ' : ON');
    ELSE
        DBMS_OUTPUT.PUT_LINE(RPAD('AUTOEXTEND for undo tablespace is',55) || ' : OFF');
    END IF;
    DBMS_OUTPUT.PUT_LINE(RPAD('Current undo retention',55) || ' : ' || v_undo_retention);

    IF v_undo_guarantee THEN
        DBMS_OUTPUT.PUT_LINE(RPAD('UNDO GUARANTEE is set to',55) || ' : TRUE');
    ELSE
        dbms_output.put_line(RPAD('UNDO GUARANTEE is set to',55) || ' : FALSE');
    END IF;
    DBMS_OUTPUT.PUT_LINE(CHR(9));

    SELECT instance_number INTO v_instance_number FROM V$INSTANCE;

    DBMS_OUTPUT.PUT_LINE('Undo Advisor Summary');
    DBMS_OUTPUT.PUT_LINE('---------------------------');

    v_undo_advisor_advice := dbms_undo_adv.undo_advisor(v_analyse_start_time, v_analyse_end_time, v_instance_number);
    DBMS_OUTPUT.PUT_LINE(v_undo_advisor_advice);

    DBMS_OUTPUT.PUT_LINE(CHR(9));
    DBMS_OUTPUT.PUT_LINE('Undo Space Recommendation');
    DBMS_OUTPUT.PUT_LINE('-------------------------');

    v_undo_health_ret := dbms_undo_adv.undo_health(v_analyse_start_time, v_analyse_end_time, v_problem, v_recommendation, v_rationale, v_retention, v_utbsize);
    IF v_undo_health_ret > 0 THEN
        DBMS_OUTPUT.PUT_LINE('Minimum Recommendation           : ' || v_recommendation);
        DBMS_OUTPUT.PUT_LINE('Rationale                        : ' || v_rationale);
        DBMS_OUTPUT.PUT_LINE('Recommended Undo Tablespace Size : ' || v_utbsize || 'M');
    ELSE
        DBMS_OUTPUT.PUT_LINE('Allocated undo space is sufficient for the current workload.');
    END IF;
  
    SELECT dbms_undo_adv.best_possible_retention(v_analyse_start_time, v_analyse_end_time) into v_best_retention FROM dual;
    SELECT dbms_undo_adv.longest_query(v_analyse_start_time, v_analyse_end_time) into v_longest_query FROM dual;
    SELECT dbms_undo_adv.required_retention(v_analyse_start_time, v_analyse_end_time) into v_required_retention FROM dual;

    DBMS_OUTPUT.PUT_LINE(CHR(9));
    DBMS_OUTPUT.PUT_LINE('Retention Recommendation');
    DBMS_OUTPUT.PUT_LINE('------------------------');
    DBMS_OUTPUT.PUT_LINE(RPAD('The best possible retention with current configuration is ',60) || ' : ' || v_best_retention || ' Seconds');
    DBMS_OUTPUT.PUT_LINE(RPAD('The longest running query ran for ',60) || ' : ' || v_longest_query || ' Seconds');
    DBMS_OUTPUT.PUT_LINE(RPAD('The undo retention required to avoid errors is ',60) || ' : ' || v_required_retention || ' Seconds');

END;
/

Sample Output

- Undo Analysis started at : 30/08/2013 11:08:40 -
--------------------------------------------------
NOTE:The following analysis is based upon the database workload during the period -
Begin Time : 23/08/2013 11:08:40
End Time   : 30/08/2013 11:08:40

Current Undo Configuration
--------------------------
Current undo tablespace                                 : UNDOTBS2
Current undo tablespace size (datafile size now)        : 20M
Current undo tablespace size (consider autoextend)      : 20M
AUTOEXTEND for undo tablespace is                       : ON
Current undo retention                                  : 900
UNDO GUARANTEE is set to                                : FALSE

Undo Advisor Summary
---------------------------
Finding 1:Undo Tablespace is under pressure. Recommendation 1:Size undo tablespace to 26 MB

Undo Space Recommendation
-------------------------
Minimum Recommendation           : Size undo tablespace to 26 MB
Rationale                        : Increase undo tablespace size so that long running queries will not fail
Recommended Undo Tablespace Size : 26M

Retention Recommendation
------------------------
The best possible retention with current configuration is    : 9171 Seconds
The longest running query ran for                            : 2543 Seconds
The undo retention required to avoid errors is               : 2543 Seconds

PL/SQL procedure successfully completed.