{"id":4888,"date":"2015-06-12T08:01:13","date_gmt":"2015-06-12T06:01:13","guid":{"rendered":"https:\/\/www.dbi-services.com\/blog\/how-to-disable-a-sql-plan-directive-permanently\/"},"modified":"2015-06-12T08:01:13","modified_gmt":"2015-06-12T06:01:13","slug":"how-to-disable-a-sql-plan-directive-permanently","status":"publish","type":"post","link":"https:\/\/www.dbi-services.com\/blog\/how-to-disable-a-sql-plan-directive-permanently\/","title":{"rendered":"How to disable a SQL Plan Directive permanently"},"content":{"rendered":"

By Franck Pachot<\/h2>\n

.
\nIn 12c you will see a lot of SQL Plan Directives. Some are useful to get better execution plans, but some will trigger too much Adaptive Dynamic Sampling and that can become a big overhead, especially in Standard Edition. Then you don’t want to drop them – or they will reappear. You can disable them, but what will happen after the retention weeks? Let’s test it.<\/p>\n

Disabled directive<\/h3>\n

A directive has been created which triggers too expensive dynamic sampling. You don’t want that and you have disabled it one year ago with:<\/p>\n

SQL> dbms_spd.alter_sql_plan_directive(14130932452940503769,'ENABLED','NO');\n<\/code><\/pre>\n
and everything is good. You’re happy with that. Here is the directive:<\/p>\n
SQL> select directive_id,state,last_used,auto_drop,enabled,extract(notes,'\/spd_note\/spd_text\/text()') spd_text,extract(notes,'\/spd_note\/internal_state\/text()') internal_state from dba_sql_plan_directives where directive_id in(select directive_id from dba_sql_plan_dir_objects where owner='DEMO' );\n\n        DIRECTIVE_ID STATE      LAST_USED AUTO_DROP ENABLED SPD_TEXT                         INTERNAL_S\n-------------------- ---------- --------- --------- ------- -------------------------------- ----------\n14130932452940503769 SUPERSEDED 28-APR-14 YES       NO      {E(DEMO.DEMO_TABLE)[A, B, C, D]} HAS_STATS\n<\/code><\/pre>\n
The directive has not been used since April 2014 thanks to the ‘enabled’ set to NO.<\/p>\n
If I run a query with a filter on those columns:<\/p>\n
SQL> select count(*) Q1 from DEMO_TABLE where a+b=c+d;\n\n                  Q1\n--------------------\n               10000\n\n23:10:32 SQL> select * from table(dbms_xplan.display_cursor(format=>'basic +note'));\n\nPLAN_TABLE_OUTPUT\n------------------------------------------------------------------------------------\nEXPLAINED SQL STATEMENT:\n------------------------\nselect count(*) Q1 from DEMO_TABLE where a+b=c+d\n\nPlan hash value: 1839825454\n\n-----------------------------------------\n| Id  | Operation          | Name       |\n-----------------------------------------\n|   0 | SELECT STATEMENT   |            |\n|   1 |  SORT AGGREGATE    |            |\n|   2 |   TABLE ACCESS FULL| DEMO_TABLE |\n-----------------------------------------\n\n<\/code><\/pre>\n
there is no dynamic sampling that this is exactly what I want.<\/p>\n
Retention weeks<\/h3>\n
My retention is the default: 53 weeks. Let’s see what happens after 53 weeks. I can call the ‘auto drop’ job with dbms_spd.drop_sql_plan_directive passing a null instead of a directive_id:<\/p>\n
SQL> exec dbms_spd.drop_sql_plan_directive(null);\n\nPL\/SQL procedure successfully completed.\n<\/code><\/pre>\n
Run a few queries<\/h3>\n
Then let’s have a few queries on those table columns:<\/p>\n
SQL> select count(*) Q2 from DEMO_TABLE where a+b=c+d;\n\n                  Q2\n--------------------\n               10000\n\nSQL> select count(*) Q3 from DEMO_TABLE where a+b=c+d;\n\n                  Q3\n--------------------\n               10000\n\n<\/code><\/pre>\n
and check the execution plan:<\/p>\n
SQL> select * from table(dbms_xplan.display_cursor(format=>'basic +note'));\n\nPLAN_TABLE_OUTPUT\n--------------------------------------------------------------------------\nEXPLAINED SQL STATEMENT:\n------------------------\nselect count(*) Q3 from DEMO_TABLE where a+b=c+d\n\nPlan hash value: 1839825454\n\n-----------------------------------------\n| Id  | Operation          | Name       |\n-----------------------------------------\n|   0 | SELECT STATEMENT   |            |\n|   1 |  SORT AGGREGATE    |            |\n|   2 |   TABLE ACCESS FULL| DEMO_TABLE |\n-----------------------------------------\n\nNote\n-----\n   - dynamic statistics used: dynamic sampling (level=2)\n   - 1 Sql Plan Directive used for this statement\n\n<\/code><\/pre>\n
A directive has been used:<\/p>\n
 SQL> select directive_id,state,last_used,auto_drop,enabled,extract(notes,'\/spd_note\/spd_text\/text()') spd_text,extract(notes,'\/spd_note\/internal_state\/text()') internal_state from dba_sql_plan_directives where directive_id in(select directive_id from dba_sql_plan_dir_objects where owner='DEMO' );\n\n        DIRECTIVE_ID STATE      LAST_USED AUTO_DROP ENABLED SPD_TEXT                         INTERNAL_S\n-------------------- ---------- --------- --------- ------- -------------------------------- ----------\n14130932452940503769 SUPERSEDED 15-MAY-15 YES       YES     {E(DEMO.DEMO_TABLE)[A, B, C, D]} HAS_STATS\n<\/code><\/pre>\n
Oh! The directive is back and enabled !<\/p>\n
Auto Drop<\/h3>\n
Here are the criteria for auto-drop. SPD are considered to be dropped when AUTO_DROP is YES and either:<\/p>\n
    \n
  • SPD is flagged as redundant<\/li>\n
  • One of the tables has been dropped (in recycle_bin means dropped)<\/li>\n
  • LAST_USAGE is from before the retention window<\/li>\n
  • State is NEW (LAST_USED is null) and CREATED is before retention window<\/li>\n<\/ul>\n
    Do you see? Nothing about the ENABLE YES\/NO there…<\/p>\n
    Conclusion<\/h3>\n
    If you want to disable a SPD and be sure that it will never reappear then you have to do both of following:<\/p>\n
    SQL> exec dbms_spd.alter_sql_plan_directive(14130932452940503769,'ENABLED','NO');\nSQL> exec dbms_spd.alter_sql_plan_directive(14130932452940503769,'AUTO_DROP','NO');\n<\/code><\/pre>\n
    then because the AUTO DROP is disabled, the directive will never be deleted automatically.<\/p>\n","protected":false},"excerpt":{"rendered":"
    By Franck Pachot . In 12c you will see a lot of SQL Plan Directives. Some are useful to get better execution plans, but some will trigger too much Adaptive Dynamic Sampling and that can become a big overhead, especially in Standard Edition. Then you don’t want to drop them – or they will reappear. […]<\/p>\n","protected":false},"author":27,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[198,59],"tags":[209,67],"type_dbi":[],"class_list":["post-4888","post","type-post","status-publish","format-standard","hentry","category-database-management","category-oracle","tag-oracle-12c","tag-performance"],"acf":[],"yoast_head":"\nHow to disable a SQL Plan Directive permanently - dbi Blog<\/title>\n<meta name=\"description\" content=\"If you want to disable a SPD the you probably want to disable AUTO DROP as well\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.dbi-services.com\/blog\/how-to-disable-a-sql-plan-directive-permanently\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"How to disable a SQL Plan Directive permanently\" \/>\n<meta property=\"og:description\" content=\"If you want to disable a SPD the you probably want to disable AUTO DROP as well\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.dbi-services.com\/blog\/how-to-disable-a-sql-plan-directive-permanently\/\" \/>\n<meta property=\"og:site_name\" content=\"dbi Blog\" \/>\n<meta property=\"article:published_time\" content=\"2015-06-12T06:01:13+00:00\" \/>\n<meta name=\"author\" content=\"Oracle Team\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Oracle Team\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"4 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\\\/\\\/www.dbi-services.com\\\/blog\\\/how-to-disable-a-sql-plan-directive-permanently\\\/#article\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.dbi-services.com\\\/blog\\\/how-to-disable-a-sql-plan-directive-permanently\\\/\"},\"author\":{\"name\":\"Oracle Team\",\"@id\":\"https:\\\/\\\/www.dbi-services.com\\\/blog\\\/#\\\/schema\\\/person\\\/66ab87129f2d357f09971bc7936a77ee\"},\"headline\":\"How to disable a SQL Plan Directive permanently\",\"datePublished\":\"2015-06-12T06:01:13+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\\\/\\\/www.dbi-services.com\\\/blog\\\/how-to-disable-a-sql-plan-directive-permanently\\\/\"},\"wordCount\":333,\"commentCount\":0,\"keywords\":[\"Oracle 12c\",\"Performance\"],\"articleSection\":[\"Database management\",\"Oracle\"],\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"CommentAction\",\"name\":\"Comment\",\"target\":[\"https:\\\/\\\/www.dbi-services.com\\\/blog\\\/how-to-disable-a-sql-plan-directive-permanently\\\/#respond\"]}]},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.dbi-services.com\\\/blog\\\/how-to-disable-a-sql-plan-directive-permanently\\\/\",\"url\":\"https:\\\/\\\/www.dbi-services.com\\\/blog\\\/how-to-disable-a-sql-plan-directive-permanently\\\/\",\"name\":\"How to disable a SQL Plan Directive permanently - 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