{"id":20,"date":"2015-12-05T12:10:03","date_gmt":"2015-12-05T18:10:03","guid":{"rendered":"http:\/\/www.aamirharoon.com\/?p=20"},"modified":"2015-12-05T12:10:03","modified_gmt":"2015-12-05T18:10:03","slug":"flush-sql-cursor-cache-oracle-library-cache","status":"publish","type":"post","link":"http:\/\/www.aamirharoon.com\/?p=20","title":{"rendered":"How to Flush SQL Cursor Cache from Oracle Library Cache"},"content":{"rendered":"
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All most all of Oracle DBAs are familiar with command to flush shared pool: alter system flush shared_pool;<\/span><\/p>\n<\/div>\n

This command clears all data from shared pool in system global area (SGA). \u00a0The shared pool stores cached data dictionary information and shared SQL and PL\/SQL areas of SQL Statements, stored procedures, packages, functions and triggers.<\/p>\n

 <\/p>\n

\"Library<\/a><\/p>\n

 <\/p>\n

This command is handy for dev, test or performance environments. \u00a0But what if you want to only flush a single SQL Cursor cache? \u00a0What if the environment is Production and a program (like Informatica) is stuck using bad explain plan and you want only flush this one SQL Cursor cache so optimizer can hard parse again and pick up a different explain plain?<\/p>\n

\n

To flush the cursor cache from Library Cache, you\u2019ll need SQL ID of the query\/cursor you want to flush.<\/p>\n<\/div>\n

Use the SQL ID to get address of the handle to the parent for this cursor and hash value of the parent statement in the library cache from\u00a0v$sqlarea<\/span> view.<\/span><\/div>\n
<\/div>\n
<\/div>\n
\n
SQL> select address, hash_value \r\nfrom v$sqlarea \r\nwhere sql_id in ('0wdq0hfrj4qxk');\r\n\r\nADDRESS          HASH_VALUE\r\n---------------- ----------\r\n\r\n0700000C5480FE90 804411656\r\n<\/pre>\n
\n
Use these 2 values to purge the cursor cache. 2nd<\/sup> parameter can be anything except ‘P’ or ‘p’ or ‘Q’ or ‘q’ or ‘R’ or ‘r’ or ‘T’ or ‘t’.<\/span><\/p>\n<\/div>\n
<\/div>\n
SQL> exec dbms_shared_pool.purge('0700000C5480FE90, 804411656','C'<\/span>);\r\n\r\nPL\/SQL procedure successfully completed.\r\n<\/pre>\n<\/div>\n
<\/div>\n
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Verify that cursor cache has been cleared.<\/span><\/span><\/p>\n<\/div>\n
<\/div>\n
\n
SQL> select address, hash_value \r\nfrom v$sqlarea \r\nwhere sql_id in ('0wdq0hfrj4qxk');\r\n\r\nno rows selected\r\n<\/pre>\n<\/div>\n
<\/div>\n
\n
You can also run the following to generate purge sql:<\/span><\/span><\/p>\n<\/div>\n
<\/div>\n
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SELECT 'exec dbms_shared_pool.purge(''' || ADDRESS || ',' || HASH_VALUE || ''',''C'');' \r\nFROM V$SQLAREA \r\nWHERE SQL_TEXT LIKE 'SELECT col1 from tab1%';\r\n\r\nSELECT 'exec dbms_shared_pool.purge(''' || ADDRESS || ',' || HASH_VALUE || ''',''C'');' \r\nFROM V$SQLAREA \r\nwhere sql_id in ('0wdq0hfrj4qxk');\r\n<\/pre>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
All most all of Oracle DBAs are familiar with command to flush shared pool: alter system flush shared_pool; This command clears all data from shared<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3,4],"tags":[30,33,31,32,28,29],"class_list":["post-20","post","type-post","status-publish","format-standard","hentry","category-11gr2","category-12cr1","tag-cache","tag-explain-plan","tag-oracle","tag-performance","tag-sql","tag-sql-cursor"],"yoast_head":"\nHow to Flush SQL Cursor Cache from Oracle Library Cache - The Database Handyman<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"http:\/\/www.aamirharoon.com\/?p=20\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"How to Flush SQL Cursor Cache from Oracle Library Cache - 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