Oracle Scratchpad

November 17, 2019

Library Cache Stats

Filed under: Oracle,Troubleshooting — Jonathan Lewis @ 9:36 am GMT Nov 17,2019

In resonse to a comment that one of my notes references a call to a packate “snap_libcache”, I’ve posted this version of SQL that can be run by SYS to create the package, with a public synonym, and privileges granted to public to execute it. The package doesn’t report the DLM (RAC) related activity, and is suitable only for 11g onwards (older versions require a massive decode of an index value to convert indx numbers into names).

rem
rem Script: snap_11_libcache.sql
rem Author: Jonathan Lewis
rem Dated: March 2001 (updated for 11g)
rem Purpose: Package to get snapshot start and delta of library cache stats
rem
rem Notes
rem Lots of changes needed by 11.2.x.x where x$kglst holds
rem two types – TYPE (107) and NAMESPACE (84) – but no
rem longer needs a complex decode.
rem
rem Has to be run by SYS to create the package
rem
rem Usage:
rem set serveroutput on size 1000000 format wrapped
rem set linesize 144
rem set trimspool on
rem execute snap_libcache.start_snap
rem — do something
rem execute snap_libcache.end_snap
rem

create or replace package snap_libcache as
procedure start_snap;
procedure end_snap;
end;
/

create or replace package body snap_libcache as

cursor c1 is
select
indx,
kglsttyp lib_type,
kglstdsc name,
kglstget gets,
kglstght get_hits,
kglstpin pins,
kglstpht pin_hits,
kglstrld reloads,
kglstinv invalidations,
kglstlrq dlm_lock_requests,
kglstprq dlm_pin_requests,
— kglstprl dlm_pin_releases,
— kglstirq dlm_invalidation_requests,
kglstmiv dlm_invalidations
from x$kglst
;

type w_type1 is table of c1%rowtype index by binary_integer;
w_list1 w_type1;
w_empty_list w_type1;

m_start_time date;
m_start_flag char(1);
m_end_time date;

procedure start_snap is
begin

m_start_time := sysdate;
m_start_flag := ‘U’;
w_list1 := w_empty_list;

for r in c1 loop
w_list1(r.indx).gets := r.gets;
w_list1(r.indx).get_hits := r.get_hits;
w_list1(r.indx).pins := r.pins;
w_list1(r.indx).pin_hits := r.pin_hits;
w_list1(r.indx).reloads := r.reloads;
w_list1(r.indx).invalidations := r.invalidations;
end loop;

end start_snap;

procedure end_snap is
begin

m_end_time := sysdate;

dbms_output.put_line(‘———————————‘);
dbms_output.put_line(‘Library Cache – ‘ ||
to_char(m_end_time,’dd-Mon hh24:mi:ss’)
);

if m_start_flag = ‘U’ then
dbms_output.put_line(‘Interval:- ‘ ||
trunc(86400 * (m_end_time – m_start_time)) ||
‘ seconds’
);
else
dbms_output.put_line(‘Since Startup:- ‘ ||
to_char(m_start_time,’dd-Mon hh24:mi:ss’)
);
end if;

dbms_output.put_line(‘———————————‘);

dbms_output.put_line(
rpad(‘Type’,10) ||
rpad(‘Description’,41) ||
lpad(‘Gets’,12) ||
lpad(‘Hits’,12) ||
lpad(‘Ratio’,6) ||
lpad(‘Pins’,12) ||
lpad(‘Hits’,12) ||
lpad(‘Ratio’,6) ||
lpad(‘Invalidations’,14) ||
lpad(‘Reloads’,10)
);

dbms_output.put_line(
rpad(‘—–‘,10) ||
rpad(‘—–‘,41) ||
lpad(‘—-‘,12) ||
lpad(‘—-‘,12) ||
lpad(‘—–‘,6) ||
lpad(‘—-‘,12) ||
lpad(‘—-‘,12) ||
lpad(‘—–‘,6) ||
lpad(‘————-‘,14) ||
lpad(‘——‘,10)
);

for r in c1 loop
if (not w_list1.exists(r.indx)) then
w_list1(r.indx).gets := 0;
w_list1(r.indx).get_hits := 0;
w_list1(r.indx).pins := 0;
w_list1(r.indx).pin_hits := 0;
w_list1(r.indx).invalidations := 0;
w_list1(r.indx).reloads := 0;
end if;

if (
(w_list1(r.indx).gets != r.gets)
or (w_list1(r.indx).get_hits != r.get_hits)
or (w_list1(r.indx).pins != r.pins)
or (w_list1(r.indx).pin_hits != r.pin_hits)
or (w_list1(r.indx).invalidations != r.invalidations)
or (w_list1(r.indx).reloads != r.reloads)
) then

dbms_output.put(rpad(substr(r.lib_type,1,10),10));
dbms_output.put(rpad(substr(r.name,1,41),41));
dbms_output.put(to_char(
r.gets – w_list1(r.indx).gets,
‘999,999,990’)
);
dbms_output.put(to_char(
r.get_hits – w_list1(r.indx).get_hits,
‘999,999,990’));
dbms_output.put(to_char(
(r.get_hits – w_list1(r.indx).get_hits)/
greatest(
r.gets – w_list1(r.indx).gets,
1
),
‘999.0’));
dbms_output.put(to_char(
r.pins – w_list1(r.indx).pins,
‘999,999,990’)
);
dbms_output.put(to_char(
r.pin_hits – w_list1(r.indx).pin_hits,
‘999,999,990’));
dbms_output.put(to_char(
(r.pin_hits – w_list1(r.indx).pin_hits)/
greatest(
r.pins – w_list1(r.indx).pins,
1
),
‘999.0’));
dbms_output.put(to_char(
r.invalidations – w_list1(r.indx).invalidations,
‘9,999,999,990’)
);
dbms_output.put(to_char(
r.reloads – w_list1(r.indx).reloads,
‘9,999,990’)
);
dbms_output.new_line;
end if;

end loop;

end end_snap;

begin
select
startup_time, ‘S’
into
m_start_time, m_start_flag
from
v$instance;

end snap_libcache;
/

drop public synonym snap_libcache;
create public synonym snap_libcache for snap_libcache;
grant execute on snap_libcache to public;

You’ll note that there are two classes of data, “namespace” and “type”. The dynamic view v$librarycache reports only the namespace rows.

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