CURSOR_SHARING determines what kind of SQL statements can share the same cursors.Example:
SET TIMI ON
SHOW PARAMETER CURSOR_SHARING
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
cursor_sharing string EXACT
SQL> ALTER SYSTEM FLUSH SHARED_POOL;
System altered.
Elapsed: 00:00:00.18
SQL> ALTER SYSTEM FLUSH BUFFER_CACHE;
System altered.
Elapsed: 00:00:10.37
SQL> CONN
Connected.
SQL> SELECT * FROM EMP WHERE DEPTNO=10;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
9001 SCOTT ANALYST 1500 10
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7839 KING PRESIDENT 17-NOV-81 5000 10
7934 MILLER CLERK 7782 23-JAN-82 1300 10
Elapsed: 00:00:00.06
SQL> SELECT * FROM EMP WHERE DEPTNO=20;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7369 SMITH CLERK 7902 17-DEC-80 800 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7902 FORD ANALYST 7566 03-DEC-81 3000 20
Elapsed: 00:00:00.01
SQL> SELECT * FROM EMP WHERE DEPTNO=30;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7900 JAMES CLERK 7698 03-DEC-81 950 30
6 rows selected.
Elapsed: 00:00:00.01
SQL> SELECT * FROM EMP WHERE DEPTNO=40;
no rows selected
Elapsed: 00:00:00.00
SQL>
SQL>
SQL> CONN
Connected.
SQL> DESC v$SQL
Name Null? Type
----------------------------------------------------------- -------- -----------------------------------------
SQL_TEXT VARCHAR2(1000)
SQL_FULLTEXT CLOB
SQL_ID VARCHAR2(13)
SHARABLE_MEM NUMBER
PERSISTENT_MEM NUMBER
RUNTIME_MEM NUMBER
SORTS NUMBER
LOADED_VERSIONS NUMBER
OPEN_VERSIONS NUMBER
USERS_OPENING NUMBER
FETCHES NUMBER
EXECUTIONS NUMBER
PX_SERVERS_EXECUTIONS NUMBER
END_OF_FETCH_COUNT NUMBER
USERS_EXECUTING NUMBER
LOADS NUMBER
FIRST_LOAD_TIME VARCHAR2(19)
INVALIDATIONS NUMBER
PARSE_CALLS NUMBER
DISK_READS NUMBER
DIRECT_WRITES NUMBER
BUFFER_GETS NUMBER
APPLICATION_WAIT_TIME NUMBER
CONCURRENCY_WAIT_TIME NUMBER
CLUSTER_WAIT_TIME NUMBER
USER_IO_WAIT_TIME NUMBER
PLSQL_EXEC_TIME NUMBER
JAVA_EXEC_TIME NUMBER
ROWS_PROCESSED NUMBER
COMMAND_TYPE NUMBER
OPTIMIZER_MODE VARCHAR2(10)
OPTIMIZER_COST NUMBER
OPTIMIZER_ENV RAW(797)
OPTIMIZER_ENV_HASH_VALUE NUMBER
PARSING_USER_ID NUMBER
PARSING_SCHEMA_ID NUMBER
PARSING_SCHEMA_NAME VARCHAR2(30)
KEPT_VERSIONS NUMBER
ADDRESS RAW(4)
TYPE_CHK_HEAP RAW(4)
HASH_VALUE NUMBER
OLD_HASH_VALUE NUMBER
PLAN_HASH_VALUE NUMBER
CHILD_NUMBER NUMBER
SERVICE VARCHAR2(64)
SERVICE_HASH NUMBER
MODULE VARCHAR2(64)
MODULE_HASH NUMBER
ACTION VARCHAR2(64)
ACTION_HASH NUMBER
SERIALIZABLE_ABORTS NUMBER
OUTLINE_CATEGORY VARCHAR2(64)
CPU_TIME NUMBER
ELAPSED_TIME NUMBER
OUTLINE_SID NUMBER
CHILD_ADDRESS RAW(4)
SQLTYPE NUMBER
REMOTE VARCHAR2(1)
OBJECT_STATUS VARCHAR2(19)
LITERAL_HASH_VALUE NUMBER
LAST_LOAD_TIME VARCHAR2(19)
IS_OBSOLETE VARCHAR2(1)
CHILD_LATCH NUMBER
SQL_PROFILE VARCHAR2(64)
PROGRAM_ID NUMBER
PROGRAM_LINE# NUMBER
EXACT_MATCHING_SIGNATURE NUMBER
FORCE_MATCHING_SIGNATURE NUMBER
LAST_ACTIVE_TIME DATE
BIND_DATA RAW(2000)
SQL> SELECT SQL_TEXT FROM v$SQL WHERE SQL_TEXT LIKE '%SELECT%*%FROM%EMP%';
SQL_TEXT
---------------------------------------------------------------------------------------------------------------
SELECT * FROM EMP WHERE DEPTNO=20
SELECT * FROM EMP WHERE DEPTNO=40
SELECT * FROM EMP WHERE DEPTNO=30
SELECT * FROM EMP WHERE DEPTNO=10
SELECT SQL_TEXT FROM v$SQL WHERE SQL_TEXT LIKE '%SELECT%*%FROM%EMP%'
Elapsed: 00:00:00.03
SQL>
SQL>
SQL>
SQL> ALTER SYSTEM SET cursor_sharing=SIMILAR;
System altered.
Elapsed: 00:00:00.12
SQL>
SQL>
SQL> CONN
Connected.
SQL> SELECT * FROM EMP WHERE EMPNO=7788;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
Elapsed: 00:00:00.01
SQL> SELECT * FROM EMP WHERE EMPNO=7839;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7839 KING PRESIDENT 17-NOV-81 5000 10
Elapsed: 00:00:00.00
SQL> SELECT * FROM EMP WHERE EMPNO=9002;
no rows selected
Elapsed: 00:00:00.00
SQL> SELECT * FROM EMP WHERE EMPNO=9001;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
9001 SCOTT ANALYST 1500 10
Elapsed: 00:00:00.00
SQL> CONN
Connected.
SQL> SELECT SQL_TEXT FROM v$SQL WHERE SQL_TEXT LIKE '%SELECT%*%FROM%EMP%';
SQL_TEXT
---------------------------------------------------------------------------------------------------------------
SELECT * FROM EMP WHERE DEPTNO=20
SELECT * FROM EMP WHERE DEPTNO=40
SELECT * FROM EMP WHERE DEPTNO=30
SELECT * FROM EMP WHERE EMPNO=:"SYS_B_0"
SELECT * FROM EMP WHERE DEPTNO=10
SELECT SQL_TEXT FROM v$SQL WHERE SQL_TEXT LIKE '%SELECT%*%FROM%EMP%'
6 rows selected.
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