Where’s my Oracle SQL Plan Baseline?
18/03/2019 2 Comments
No so long ago I was having fun creating SQL Plan Baselines in a old 11.2.0.3 database due to be decomissioned but which needs to keep running for a while (no doubt several years) – so minimal time/money to be expended on it. Then, one day, I couldn’t create a baseline and needed to figure out why…
We get the occasional painful plan change, so pinning down an acceptable historic plan using a Baseline is becoming a regular occurrence. The standard route for this is:
1. Notice plan isn’t good and that we have been running with a good plan historically
2. Identify an plan hash value which is acceptable
3. Load it from the library cache if that plan is in there (unlikely)
[ Kerry Osborne has a useful blog post/script for this so I won’t reproduce here: http://kerryosborne.oracle-guy.com/2012/03/displaying-sql-baseline-plans/ ]
4. If not, create a SQL Tuning Set from AWR with that specific plan and convert the SQL Tuning Set into a Baseline. You will need the begin-and-end snap id’s containing the plan, the sql_id and the plan_hash_value for the specific plan you want to baseline:
Please ensure you have suitable licensing before running any of the following code!
declare
baseline_ref_cur DBMS_SQLTUNE.SQLSET_CURSOR;
begin
DBMS_SQLTUNE.CREATE_SQLSET('NEIL');
open baseline_ref_cur for
select VALUE(p) from table(
DBMS_SQLTUNE.SELECT_WORKLOAD_REPOSITORY(&begin_snap_id, &end_snap_id,'sql_id='||CHR(39)||'4jcxvz3adqbs2'||CHR(39)||'and plan_hash_value=1905606778',NULL,NULL,NULL,NULL,NULL,NULL,'ALL')) p;
DBMS_SQLTUNE.LOAD_SQLSET('NEIL', baseline_ref_cur);
end;
/
Did we get it?
select * from dba_sqlset_statements where sqlset_name = 'NEIL'; SQLSET_NAME, SQLSET_OWNER, SQLSET_ID, SQL_ID, FORCE_MATCHING_SIGNATURE, SQL_TEXT, PARSING_SCHEMA_NAME, PLAN_HASH_VALUE ... ---------------------------------------------------------------------------------------------------------------------------------------------------------- NEIL NEIL_DBA 35 4jcxvz3adqbs2 6134983393191283611 INSERT WHEN CNT = 1 THEN INTO SOME_TABLE... APP 1905606778 ...
Cool! I have captured the SQL. Lets create the baseline using: dbms_spm.load_plans_from_sqlset
declare
cnt number;
begin
cnt := dbms_spm.load_plans_from_sqlset(sqlset_name=>'NEIL',SQLSET_OWNER=>'NEIL_DBA');
dbms_output.put_line('Plans Loaded : '||to_char(cnt));
end;
/
... and I get ...
Plans Loaded : 0
Zero plans? So what plans are in there? Has my plan actually appeared?
select SQL_HANDLE,PLAN_NAME,CREATOR,ORIGIN,PARSING_SCHEMA_NAME, ENABLED,ACCEPTED,REPRODUCED,CREATED
from dba_sql_plan_baselines where origin like 'MANUAL-LOAD%' order by created desc;
SQL_HANDLE PLAN_NAME CREATOR ORIGIN PARSING_SCHEMA_NAME ENABLED ACCEPTED REPRODUCED CREATED
-----------------------------------------------------------------------------------------------------------------------------------------------------------
SQL_23829f7bf3712438 SQL_PLAN_270nzggtr291s1a6ce30c NEIL_DBA MANUAL-LOAD APP YES YES YES 2018-12-31 00.00.00.000000000
No! But how do I prove that? Baselines don’t have the SQL ID associated with them?
Here’s some code from [blog post here: http://oracleprof.blogspot.com/2011/07/how-to-find-sqlid-and-planhashvalue-in.html ] which will take the SQL_Handle and display the SQL ID and Plan Hash Value (you may need an explicit grant to use DBMS_CRYPTO in your PDB for this to work):
For SQL Handle: SQL_23829f7bf3712438 declare v_sqlid VARCHAR2(13); v_num number; BEGIN dbms_output.put_line('SQL_ID '||' '|| 'PLAN_HASH_VALUE' || ' ' || 'SQL_HANDLE ' || ' ' || 'PLAN_NAME'); dbms_output.put_line('-------------'||' '|| '---------------' || ' ' || '------------------------------' || ' ' || '--------------------------------'); for a in (select sql_handle, plan_name, trim(substr(g.PLAN_TABLE_OUTPUT,instr(g.PLAN_TABLE_OUTPUT,':')+1)) plan_hash_value, sql_text from (select t.*, c.sql_handle, c.plan_name, c.sql_text from dba_sql_plan_baselines c, table(dbms_xplan.DISPLAY_SQL_PLAN_BASELINE(c.sql_handle, c.plan_name)) t where c.sql_handle = '&sql_handle') g where PLAN_TABLE_OUTPUT like 'Plan hash value%') loop v_num := to_number(sys.UTL_RAW.reverse(sys.UTL_RAW.SUBSTR(dbms_crypto.hash(src => UTL_I18N.string_to_raw(a.sql_text || chr(0),'AL32UTF8'), typ => 2),9,4)) || sys.UTL_RAW.reverse(sys.UTL_RAW.SUBSTR(dbms_crypto.hash(src => UTL_I18N.string_to_raw(a.sql_text || chr(0),'AL32UTF8'), typ => 2),13,4)),RPAD('x', 16, 'x')); v_sqlid := ''; FOR i IN 0 .. FLOOR(LN(v_num) / LN(32)) LOOP v_sqlid := SUBSTR('0123456789abcdfghjkmnpqrstuvwxyz',FLOOR(MOD(v_num / POWER(32, i), 32)) + 1,1) || v_sqlid; END LOOP; dbms_output.put_line(v_sqlid ||' ' || rpad(a.plan_hash_value,15) || ' ' || rpad(a.sql_handle,30) || ' ' || rpad(a.plan_name,30)); end loop; end; / SQL_ID PLAN_HASH_VALUE SQL_HANDLE PLAN_NAME ------------- --------------- ------------------------------ -------------------------------- 7f4n59twq8mrj 3036703685 SQL_23829f7bf3712438 SQL_PLAN_270nzggtr291s1a6ce30c
That baseline is definitely not mine. It’s for the wrong SQL ID!
The “Plans Loaded” message was correct when it said “0“!
Why? There was no error message, no output other than the number of plans loaded. That sucks dbms_spm!
I need to trace it. Do that by using dbms_spm.configure
(thank you Timur Akhmadeev for helping me! It’s not easy to google/MOS how to do this, hence this post so I don’t forget again!)
declare
cnt number;
begin
dbms_spm.configure('spm_tracing',1);
cnt := dbms_spm.load_plans_from_sqlset(sqlset_name=>'NEIL',SQLSET_OWNER=>'NEIL_DBA');
dbms_output.put_line('Plans Loaded : '||to_char(cnt));
dbms_spm.configure('spm_tracing',0);
end;
/
Looking in the trace file, it tells you what went wrong:
*** 2019-01-01 12:00:00.007 load sts: STS=NEIL, owner=NEIL_DBA load sts: cursor opened load sts: sql_id=4jcxvz3adqbs2 phv=1905606778 load sts: plan has empty outline, skipping it load sts: plans total=0 plans loaded=0
So why does my plan have an empty outline?
The SQL_TEXT began “INSERT WHEN CNT = 1 THEN INTO SOME_TABLE… “.
It’s a multi-table insert, inserting into different tables depending upon a condition.
Baselines for Multi-table Inserts are NOT supported by SPM.
https://docs.oracle.com/cd/E11882_01/server.112/e41084/statements_9014.htm#SQLRF01604
I hope this helps you with your baseline creation troubleshooting!
Having baseline creation problems, you should check MOS article 789520.1
Neil Chandler's DB Blog 