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----------------------------------------------------------------------------------------
--
-- File name: cs_mark_sql_hot.sql
--
-- Purpose: Use DBMS_SHARED_POOL.markhot to reduce contention during high concurency hard parse
--
-- Author: Carlos Sierra
--
-- Version: 2021/11/05
--
-- Usage: Execute connected to PDB.
--
-- Enter SQL_ID when requested.
--
-- Example: $ sqlplus / as sysdba
-- SQL> @cs_mark_sql_hot.sql
--
-- Notes: Developed and tested on 19c
--
-- https://jonathanlewis.wordpress.com/2017/10/02/markhot/
--
-- When a statement (through its “full_hash_value”) is marked as hot
-- an extra value visible as the property column in v$db_object_cache
-- is set to a value that seems to be dependent on the process id of the
-- session attempting to execute the statement, and this value is used as
-- an extra component in calculating a new full_hash_value (which leads
-- to a new hash_value and sql_id).
-- With a different full_hash_value the same text generates a new parent
-- cursor which is (probably) going to be associated with a new library
-- cache hash bucket and latch.
-- The property value for the original parent cursor is set to “HOT”,
-- and the extra copies become “HOTCOPY1”, “HOTCOPY2” and so on.
-- Interestingly once an object is marked as HOT and the first HOTCOPYn
-- has appeared the original version may disappear from v$sql while still
-- existing in v$db_object_cache.
--
---------------------------------------------------------------------------------------
--
@@cs_internal/cs_primary.sql
@@cs_internal/cs_cdb_warn.sql
@@cs_internal/cs_set.sql
@@cs_internal/cs_def.sql
@@cs_internal/cs_file_prefix.sql
--
DEF cs_script_name = 'cs_mark_sql_hot';
--
PRO
PRO 1. Selective SQL Text Substring: (e.g.: /* getMaxTransactionCommitID */)
DEF sql_text_substring = '&1.';
UNDEF 1;
--
SELECT '&&cs_file_prefix._&&cs_script_name.' cs_file_name FROM DUAL;
--
@@cs_internal/cs_signature.sql
--
@@cs_internal/cs_spool_head.sql
PRO SQL> @&&cs_script_name..sql "&&sql_text_substring."
@@cs_internal/cs_spool_id.sql
--
PRO SQL_TEXT_STR : "&&sql_text_substring."
--
COL hot NEW_V hot FOR 9999;
COL cold NEW_V cold FOR 9999;
COL hash_value FOR 9999999999;
COL sql_text FOR A80 TRUNC;
--
PRO
PRO BEFORE
PRO ~~~~~~
WITH
s AS (
SELECT /*+ MATERIALIZE NO_MERGE */
DISTINCT con_id, sql_id, hash_value, address, sql_text
FROM v$sql
WHERE &&cs_con_id. <> 1 -- executed on PDB and not on CDB$ROOT
AND con_id = &&cs_con_id.
AND '&&sql_text_substring.' IS NOT NULL
AND sql_text LIKE '%&&sql_text_substring.%'
AND sql_text NOT LIKE '%MATERIALIZE%' -- exclude SQL like this one!
AND object_status = 'VALID'
AND is_obsolete = 'N'
AND is_shareable = 'Y'
AND ROWNUM >= 1 /* MATERIALIZE */
)
SELECT c.full_hash_value,
SUM(CASE WHEN c.property IS NOT NULL THEN 1 ELSE 0 END) AS hot,
SUM(CASE WHEN c.property IS NULL THEN 1 ELSE 0 END) AS cold,
s.sql_id, s.hash_value, s.address, s.sql_text
FROM s, v$db_object_cache c
WHERE c.con_id = s.con_id
AND c.hash_value = s.hash_value
AND c.addr = s.address
AND c.name = s.sql_text
AND c.namespace = 'SQL AREA'
AND c.type = 'CURSOR'
AND c.status = 'VALID'
GROUP BY
c.full_hash_value, s.sql_id, s.hash_value, s.address, s.sql_text
ORDER BY
c.full_hash_value, s.sql_id, s.hash_value, s.address, s.sql_text
/
--
PRO
PRO SUMMARY
PRO ~~~~~~~
WITH
s AS (
SELECT /*+ MATERIALIZE NO_MERGE */
DISTINCT con_id, sql_id, hash_value, address, sql_text
FROM v$sql
WHERE &&cs_con_id. <> 1 -- executed on PDB and not on CDB$ROOT
AND con_id = &&cs_con_id.
AND '&&sql_text_substring.' IS NOT NULL
AND sql_text LIKE '%&&sql_text_substring.%'
AND sql_text NOT LIKE '%MATERIALIZE%' -- exclude SQL like this one!
AND object_status = 'VALID'
AND is_obsolete = 'N'
AND is_shareable = 'Y'
AND ROWNUM >= 1 /* MATERIALIZE */
)
SELECT SUM(CASE WHEN c.property IS NOT NULL THEN 1 ELSE 0 END) AS hot,
SUM(CASE WHEN c.property IS NULL THEN 1 ELSE 0 END) AS cold
FROM s, v$db_object_cache c
WHERE c.con_id = s.con_id
AND c.hash_value = s.hash_value
AND c.addr = s.address
AND c.name = s.sql_text
AND c.namespace = 'SQL AREA'
AND c.type = 'CURSOR'
AND c.status = 'VALID'
/
--
PRO
PAUSE Hit "return" to continue; or "control-c" then "return" to exit:
--
PRO
PRO MAKE HOT (IF COLD > 0 AND HOT = 0)
PRO ~~~~~~~~
SET SERVEROUT ON;
BEGIN
IF TO_NUMBER(NVL(TRIM('&&cold.'), '0')) > 0 AND TO_NUMBER(NVL(TRIM('&&hot.'), '0')) = 0 THEN -- sql has not been marked as hot
FOR i IN (
WITH
s AS (
SELECT /*+ MATERIALIZE NO_MERGE */
DISTINCT con_id, sql_id, hash_value, address, sql_text
FROM v$sql
WHERE &&cs_con_id. <> 1 -- executed on PDB and not on CDB$ROOT
AND con_id = &&cs_con_id.
AND '&&sql_text_substring.' IS NOT NULL
AND sql_text LIKE '%&&sql_text_substring.%'
AND sql_text NOT LIKE '%MATERIALIZE%' -- exclude SQL like this one!
AND object_status = 'VALID'
AND is_obsolete = 'N'
AND is_shareable = 'Y'
AND ROWNUM >= 1 /* MATERIALIZE */
)
SELECT DISTINCT full_hash_value
FROM s, v$db_object_cache c
WHERE c.con_id = s.con_id
AND c.hash_value = s.hash_value
AND c.addr = s.address
AND c.name = s.sql_text
AND c.namespace = 'SQL AREA'
AND c.type = 'CURSOR'
AND c.status = 'VALID'
AND c.property IS NULL -- COLD
)
LOOP
DBMS_OUTPUT.put_line('MARKHOT:'||i.full_hash_value);
DBMS_SHARED_POOL.markhot(hash => i.full_hash_value, namespace => 0);
END LOOP;
END IF;
END;
/
SET SERVEROUT OFF;
--
PRO
PRO SQL> @&&cs_script_name..sql "&&sql_text_substring."
--
@@cs_internal/cs_spool_tail.sql
@@cs_internal/cs_undef.sql
@@cs_internal/cs_reset.sql
--