对 Tom 的 RunStats 包的两点说明

SQL>grant select on sys.v_$timer to MyUser;

修改后的脚本(对过程名字稍稍有点调整)：

create or replace package runstats
    as
        procedure bench_start;
        procedure bench_middle;
        procedure bench_stop( p_difference_threshold in number default 0 );
    end;
/

create or replace package body runstats
as
g_start number;
g_run1  number;
g_run2  number;

procedure bench_start
is 
begin
    delete from run_stats;

    insert into run_stats 
    select 'before', stats.* from stats;
        
    g_start := dbms_utility.get_time;
end;

procedure bench_middle
is
begin
    g_run1 := (dbms_utility.get_time-g_start);
 
    insert into run_stats 
    select 'after 1', stats.* from stats;
    g_start := dbms_utility.get_time;

end;

procedure bench_stop(p_difference_threshold in number default 0)
is
begin
    g_run2 := (dbms_utility.get_time-g_start);
    --add a line here to avoid ora-20000
    dbms_output.enable(480000); 
    dbms_output.put_line
    ( 'Run1 ran in ' || g_run1 || ' hsecs' );
    dbms_output.put_line
    ( 'Run2 ran in ' || g_run2 || ' hsecs' );
    dbms_output.put_line
    ( 'run 1 ran in ' || round(g_run1/g_run2*100,2) || 
      '% of the time' );
    dbms_output.put_line( chr(9) );

    insert into run_stats 
    select 'after 2', stats.* from stats;

    dbms_output.put_line
    ( rpad( 'Name', 30 ) || lpad( 'Run1', 12 ) || 
      lpad( 'Run2', 12 ) || lpad( 'Diff', 12 ) );

    for x in 
    ( select rpad( a.name, 30 ) || 
             to_char( b.value-a.value, '999,999,999' ) || 
             to_char( c.value-b.value, '999,999,999' ) || 
             to_char( ( (c.value-b.value)-(b.value-a.value)), '999,999,999' ) data
        from run_stats a, run_stats b, run_stats c
       where a.name = b.name
         and b.name = c.name
         and a.runid = 'before'
         and b.runid = 'after 1'
         and c.runid = 'after 2'
         -- and (c.value-a.value) > 0
         and abs( (c.value-b.value) - (b.value-a.value) ) 
               > p_difference_threshold
       order by abs( (c.value-b.value)-(b.value-a.value))
    ) loop
        dbms_output.put_line( x.data );
    end loop;

    dbms_output.put_line( chr(9) );
    dbms_output.put_line
    ( 'Run1 latches total versus runs -- difference and pct' );
    dbms_output.put_line
    ( lpad( 'Run1', 12 ) || lpad( 'Run2', 12 ) || 
      lpad( 'Diff', 12 ) || lpad( 'Pct', 10 ) );

    for x in 
    ( select to_char( run1, '999,999,999' ) ||
             to_char( run2, '999,999,999' ) ||
             to_char( diff, '999,999,999' ) ||
             to_char( round( run1/run2*100,2 ), '99,999.99' ) || '%' data
        from ( select sum(b.value-a.value) run1, sum(c.value-b.value) run2,
                      sum( (c.value-b.value)-(b.value-a.value)) diff
                 from run_stats a, run_stats b, run_stats c
                where a.name = b.name
                  and b.name = c.name
                  and a.runid = 'before'
                  and b.runid = 'after 1'
                  and c.runid = 'after 2'
                  and a.name like 'LATCH%'
                )
    ) loop
        dbms_output.put_line( x.data );
    end loop;
end;

end;
/

附录:DBMS_OUTPUT.ENABLE vs SET SERVEROUTPUT ON

DBMS_OUTPUT.ENABLE enables calls to put, put_line, new_line, get_line and 
get_lines. If the dbms_output package has not been enabled, calls to these 
procedures will be ignored.

If DBMS_OUTPUT package has been enabled, calls to DBMS_OUTPUT.PUT_LINE write 
lines into the buffer. Nothing is actually displayed until the program executes
completely and control is transfered back to SQL*Plus.

SET SERVEROUTPUT ON causes that SQL*Plus use DBMS_OUTPUT.GET_LINES
to read the buffer and writes it to the terminal. When you set serveroutput  
on, DBMS_OUTPUT.ENABLE is implicitly called, with the default size of 2000.

If you want to change the default buffer size you can use:
        SET SERVEROUTPUT ON SIZE n
or 
        DBMS_OUTPUT.ENABLE(n)
 
  (where 'n' is the new buffer size) 

这两个设定之间的差别