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Oracle 獲取SQL執(zhí)行計劃方法

方法一：DBMS_XPLAN.DISPLAY_CURSOR
方法二：explain plan for ......
方法三：Tuning SQL*Plus(autotrace)
方法四：*+ gather_plan_statistics *
方法五：10046
方法六: 10053
方法七：awrsqrpt.sql
方法八：statistics_level=all

方法一：DBMS_XPLAN.DISPLAY_CURSOR 

(1)從共享池里獲取
SELECT * FROM TABLE(dbms_xplan.display_cursor('SQL_ID'));

By default, the table function DISPLAY_CURSOR formats the execution plan for the last SQL statement executed by the session.

DISPLAY_CURSOR Function
This table function displays the explain plan of any cursor loaded in the cursor cache.
In addition to the explain plan, various plan statistics (such as. I/O, memory and timing) can be reported (based on the V$SQL_PLAN_STATISTICS_ALL VIEWS).

Syntax

DBMS_XPLAN.DISPLAY_CURSOR(
   sql_id           IN  VARCHAR2  DEFAULT  NULL,
   cursor_child_no  IN  NUMBER    DEFAULT  0,
   format           IN  VARCHAR2  DEFAULT  'TYPICAL');

Example:

SYS@orcl> SELECT /* TOTO */ ename, dname FROM scott.dept d join scott.emp e USING (deptno);
14 rows selected.

SYS@orcl> SELECT sql_id, child_number FROM v$sql WHERE sql_text LIKE '%TOTO%';
--9dpnjdgna1k40            

SYS@orcl> SELECT * FROM table(DBMS_XPLAN.DISPLAY_CURSOR('9dpnjdgna1k40',0));
SQL_ID  9dpnjdgna1k40, child number 0
-------------------------------------
SELECT /* TOTO */  ename, dname   FROM scott.dept d   join scott.emp e
USING (deptno)

Plan hash value: 844388907

----------------------------------------------------------------------------------------
| Id  | Operation                    | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |         |       |       |     6 (100)|          |
|   1 |  MERGE JOIN                  |         |    14 |   308 |     6  (17)| 00:00:01 |
|   2 |   TABLE ACCESS BY INDEX ROWID| DEPT    |     4 |    52 |     2   (0)| 00:00:01 |
|   3 |    INDEX FULL SCAN           | PK_DEPT |     4 |       |     1   (0)| 00:00:01 |
|*  4 |   SORT JOIN                  |         |    14 |   126 |     4  (25)| 00:00:01 |
|   5 |    TABLE ACCESS FULL         | EMP     |    14 |   126 |     3   (0)| 00:00:01 |
----------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   4 - access("D"."DEPTNO"="E"."DEPTNO")
       filter("D"."DEPTNO"="E"."DEPTNO")

24 rows selected.

或者直接查詢：
SELECT t.* FROM v$sql s, table(DBMS_XPLAN.DISPLAY_CURSOR(s.sql_id, s.child_number)) t WHERE sql_text LIKE '%TOTO%';

優(yōu)點： 
(1)知道sql_id就可以得到執(zhí)行計劃，和explain plan for一樣無須執(zhí)行；
(2)可以得到真實執(zhí)行計劃；
缺點:
(1)沒有輸出運行時的相關統(tǒng)計信息(例如:邏輯讀，遞歸調(diào)用次數(shù)，物理讀等)
(2)無法判斷處理多少上；
(3)無法判斷表訪問多少次； 
適用：
一個SQL對應多個執(zhí)行計劃； 

方法二： explain plan for獲取

(1)EXPLAIN PLAN FOR XXX;
(2)select * from table(DBMS_XPLAN.DISPLAY);
(3)從awr性能視圖里獲取
SELECT * FROM TABLE(dbms_xplan.display_awr('SQL_ID'));

DISPLAY Function
This table function displays the contents of the plan table.

In addition, you can use this table function to display any plan (with or without statistics) stored in a table as long as the columns of this table are named the same as columns of the plan table (or V$SQL_PLAN_STATISTICS_ALL if statistics are included).
You can apply a predicate on the specified table to select rows of the plan to display.

Syntax

DBMS_XPLAN.DISPLAY(
   table_name    IN  VARCHAR2  DEFAULT 'PLAN_TABLE',
   statement_id  IN  VARCHAR2  DEFAULT  NULL,
   format        IN  VARCHAR2  DEFAULT  'TYPICAL',
   filter_preds  IN  VARCHAR2 DEFAULT NULL);
   
Example:
(1)EXPLAIN PLAN FOR XXX;
(2)select * from table(DBMS_XPLAN.DISPLAY);

SYS@orcl> 
EXPLAIN PLAN FOR
SELECT *
  FROM scott.emp e, scott.dept d
 WHERE e.deptno = d.deptno
   AND e.ename = 'CLARK';
Explained.

SYS@orcl> SET LINESIZE 130
SYS@orcl> SET PAGESIZE 0
SYS@orcl> SELECT * FROM table(DBMS_XPLAN.DISPLAY);
Plan hash value: 3625962092

----------------------------------------------------------------------------------------
| Id  | Operation                    | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |         |     1 |    58 |     4   (0)| 00:00:01 |
|   1 |  NESTED LOOPS                |         |       |       |            |          |
|   2 |   NESTED LOOPS               |         |     1 |    58 |     4   (0)| 00:00:01 |
|*  3 |    TABLE ACCESS FULL         | EMP     |     1 |    38 |     3   (0)| 00:00:01 |
|*  4 |    INDEX UNIQUE SCAN         | PK_DEPT |     1 |       |     0   (0)| 00:00:01 |
|   5 |   TABLE ACCESS BY INDEX ROWID| DEPT    |     1 |    20 |     1   (0)| 00:00:01 |
----------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   3 - filter("E"."ENAME"='CLARK')
   4 - access("E"."DEPTNO"="D"."DEPTNO")

18 rows selected.

---如果執(zhí)行計劃下方出現(xiàn)'PLAN_TABLE' is old version提示，需要重新生成plan_table;
SQL> drop table PLAN_TABLE;
SQL> @?/rdbms/admin/utlxplan.sql

優(yōu)點：
(1)無需真正的執(zhí)行，快捷方便；
缺點：
(1)沒有輸出運行時的相關統(tǒng)計信息
(產(chǎn)生多少邏輯讀，多少次遞歸調(diào)用，多少次物理讀等情況)
(2)無法判斷處理多少行；
(3)無法判斷表被訪問多少次；

適用于:
SQL執(zhí)行很長時間才出結果或返回不了結果;

方法三：Tuning SQL*Plus(autotrace)

Tracing Statements
You can automatically get a report on the execution path used by the SQL optimizer and the statement execution statistics. The report is generated after successful SQL DML (that is, SELECT, DELETE, UPDATE and INSERT) statements. It is useful for monitoring and tuning the performance of these statements.

SQL*Plus report output may differ for DML if dynamic sampling is in effect.

Controlling the Autotrace Report
You can control the report by setting the AUTOTRACE system variable.
(1)SET AUTOTRACE OFF:
No AUTOTRACE report is generated. This is the default.
(2)SET AUTOTRACE ON EXPLAIN:
The AUTOTRACE report shows only the optimizer execution path
(3)SET AUTOTRACE ON STATISTICS:
The AUTOTRACE report shows only the SQL statement execution statistics.
(4)SET AUTOTRACE ON:
The AUTOTRACE report includes both the optimizer execution path and the SQL statement execution statistics.
(5)SET AUTOTRACE TRACEONLY:
Like SET AUTOTRACE ON, but suppresses the printing of the user's query output, if any. 
If STATISTICS is enabled, query data is still fetched, but not printed.

To use this feature, you must create a PLAN_TABLE table in your schema and then have the PLUSTRACE role granted to you. 
DBA privileges are required to grant the PLUSTRACE role.
(1)Creating a PLAN_TABLE
CONNECT HR 
@$ORACLE_HOME/rdbms/admin/utlxplan.sql 
(2)Creating the PLUSTRACE Role
CONNECT / AS SYSDBA 
@$ORACLE_HOME/sqlplus/admin/plustrce.sql 
(3)Granting the PLUSTRACE Role
CONNECT / AS SYSDBA 
GRANT PLUSTRACE TO HR; 

Example:

SYS@orcl> set autotrace on
SYS@orcl> 
SELECT /* TOTO */ ename, dname FROM scott.dept d join scott.emp e USING (deptno);
 
......
14 rows selected.

Execution Plan
----------------------------------------------------------
Plan hash value: 844388907

----------------------------------------------------------------------------------------
| Id  | Operation                    | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |         |    14 |   308 |     6  (17)| 00:00:01 |
|   1 |  MERGE JOIN                  |         |    14 |   308 |     6  (17)| 00:00:01 |
|   2 |   TABLE ACCESS BY INDEX ROWID| DEPT    |     4 |    52 |     2   (0)| 00:00:01 |
|   3 |    INDEX FULL SCAN           | PK_DEPT |     4 |       |     1   (0)| 00:00:01 |
|*  4 |   SORT JOIN                  |         |    14 |   126 |     4  (25)| 00:00:01 |
|   5 |    TABLE ACCESS FULL         | EMP     |    14 |   126 |     3   (0)| 00:00:01 |
----------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   4 - access("D"."DEPTNO"="E"."DEPTNO")
       filter("D"."DEPTNO"="E"."DEPTNO")Statistics
----------------------------------------------------------
          0  recursive calls
          0  db block gets
          7  consistent gets
          0  physical reads
          0  redo size
        819  bytes sent via SQL*Net to client
        524  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          1  sorts (memory)
          0  sorts (disk)
         14  rows processed

報錯SP2-0618需要執(zhí)行plustrce.sql
SQL> conn scott/tiger
SQL> set autotrace on
SP2-0618: Cannot find the Session Identifier.  Check PLUSTRACE role is enabled
SP2-0611: Error enabling STATISTICS report

SQL> @?/sqlplus/admin/plustrce.sql
SQL> grant plustrace to scott;

優(yōu)點：
(1)可以輸出運行時的相關統(tǒng)計信息(產(chǎn)生多少邏輯讀，多少次遞歸調(diào)用，多少次物理讀)
(2)traceonly可以控制返回結果不輸出；
缺點：
(1)必須等到語句真正執(zhí)行完畢后，才可以出結果；
(2)無法看到表被訪問多少次；

方法四：*+ gather_plan_statistics *

SYS@orcl> set linesize 130
SYS@orcl> show parameter statistics_level
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
statistics_level                     string      TYPICAL

SYS@orcl> SELECT /*+ gather_plan_statistics */
 ename, dname
  FROM scott.dept d
  join scott.emp e
 USING (deptno);  

......
14 rows selected.

SYS@orcl> select * from table(dbms_xplan.display_cursor(null,null,'allstats last'));

PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------------------
SQL_ID  4y8f4mhhn471d, child number 0
-------------------------------------
SELECT /*+ gather_plan_statistics */  ename, dname   FROM scott.dept d
 join scott.emp e  USING (deptno)

Plan hash value: 844388907

-----------------------------------------------------------------------------------------------------------------------------
| Id  | Operation                    | Name    | Starts | E-Rows | A-Rows |   A-Time   | Buffers |  OMem |  1Mem | Used-Mem |
-----------------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |         |      1 |        |     14 |00:00:00.01 |       7 |       |       |          |PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------------------
|   1 |  MERGE JOIN                  |         |      1 |     14 |     14 |00:00:00.01 |       7 |       |       |          |
|   2 |   TABLE ACCESS BY INDEX ROWID| DEPT    |      1 |      4 |      4 |00:00:00.01 |       4 |       |       |          |
|   3 |    INDEX FULL SCAN           | PK_DEPT |      1 |      4 |      4 |00:00:00.01 |       2 |       |       |          |
|*  4 |   SORT JOIN                  |         |      4 |     14 |     14 |00:00:00.01 |       3 |  2048 |  2048 | 2048  (0)|
|   5 |    TABLE ACCESS FULL         | EMP     |      1 |     14 |     14 |00:00:00.01 |       3 |       |       |          |
-----------------------------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   4 - access("D"."DEPTNO"="E"."DEPTNO")PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------------------
       filter("D"."DEPTNO"="E"."DEPTNO")

24 rows selected.

(1)starts為該SQL執(zhí)行的次數(shù)；
(2)E-Rows為執(zhí)行計劃預計的行數(shù)；
(3)A-Rows為實際返回的行數(shù)。A-Rows和E-Rows做比較，就可以確定哪一步執(zhí)行計劃出了問題。
(4)A-Time為每一步實際執(zhí)行的時間(HH:MM:SS.FF),根據(jù)這一行可以知道該SQL耗時在哪個地方；
(5)buffers為每一步實際執(zhí)行的邏輯讀或一致性讀；
(6)Reads為物理讀；

優(yōu)點:
(1)可以清晰的從STARTS得出表被訪問多少次；
(2)可以清晰的從E-ROWS和A-ROWS中得到預測的行數(shù)和真實的行數(shù)，從而可以準確判斷Oracle評估是否準確；
(3)BUFFER顯示真實的邏輯讀數(shù)量；
缺點:
(1)必須要等到語句真正執(zhí)行完畢后，才能出結果；
(2)無法控制記錄不打屏輸出，沒有類似autotrace的traceonly的功能；
(3)看不出遞歸調(diào)用的次數(shù)，看不出物理讀；

適用：
獲取表被訪問的次數(shù)；

方法五：10046

(1)
設置追蹤標識符
alter session set tracefile_identifier='10046';
開啟跟蹤
alter session set events '10046 trace name context forever, level 12';
執(zhí)行語句
select count(*) from all_objects;
關閉10046追蹤
alter session set events '10046 trace name context off';

(2)
oradebug setmypid;
oradebug unlimit;
oradebug event 10046 trace name context forever ,level 12;
SELECT ename, dname FROM scott.dept d join scott.emp e USING (deptno);
oradebug  tracefile_name;
Oradebug event 10046 trace name context off;

Example 1:

SYS@orcl> alter session set tracefile_identifier='10046';
SYS@orcl> alter session set events '10046 trace name context forever, level 12';
SYS@orcl> SELECT ename, dname FROM scott.dept d join scott.emp e USING (deptno);
SYS@orcl> alter session set events '10046 trace name context off';
[oracle@uf2010813 trace]$ pwd     
/opt/oracle/app/diag/rdbms/orcl/orcl/trace

[oracle@uf2010813 trace]$ ll -rth *10046*
-rw-r-----. 1 oracle oinstall  135 Jul 31 21:55 orcl_ora_29418_10046.trm
-rw-r-----. 1 oracle oinstall 3.8K Jul 31 21:55 orcl_ora_29418_10046.trc

[oracle@uf2010813 trace]$ tkprof orcl_ora_29418_10046.trc 10046.log sys=no

Example 2:

SYS@orcl> oradebug setmypid;
SYS@orcl> oradebug unlimit;
SYS@orcl> oradebug event 10046 trace name context forever ,level 12;
SYS@orcl> SELECT ename, dname FROM scott.dept d join scott.emp e USING (deptno);
SYS@orcl> oradebug  tracefile_name;
/opt/oracle/app/diag/rdbms/orcl/orcl/trace/orcl_ora_31388.trc

SYS@orcl> Oradebug event 10046 trace name context off;
[oracle@uf2010813 trace]$ tkprof orcl_ora_31388.trc 10046.log1 sys=no

Elapsed times include waiting on following events:
  Event waited on                             Times   Max. Wait  Total Waited
  ----------------------------------------   Waited  ----------  ------------
  SQL*Net message to client                       4        0.00          0.00
  SQL*Net message from client                     4        6.17         17.25
  Disk file operations I/O                        2        0.00          0.00
  db file sequential read                         4        0.02          0.04
  
Elapsed times include waiting on following events:
  Event waited on                             Times   Max. Wait  Total Waited
  ----------------------------------------   Waited  ----------  ------------
  Disk file operations I/O                        1        0.00          0.00
  db file sequential read                        23        0.01          0.12
  asynch descriptor resize                        1        0.00          0.00

    1  user  SQL statements in session.
   66  internal SQL statements in session.
   67  SQL statements in session.
********************************************************************************
Trace file: orcl_ora_31388.trc
Trace file compatibility: 11.1.0.7
Sort options: default

       1  session in tracefile.
       1  user  SQL statements in trace file.
      66  internal SQL statements in trace file.
      67  SQL statements in trace file.
      13  unique SQL statements in trace file.
    1390  lines in trace file.
       0  elapsed seconds in trace file.

優(yōu)點:
(1)可以看出SQL語句對應的等待事件；
(2)如果SQL語句中有函數(shù)調(diào)用，函數(shù)中又有SQL，將會被列出；
(3)可以方便的看出處理的行數(shù)，產(chǎn)生的物理讀，邏輯讀；
(4)可以方便的看出解析時間和執(zhí)行計劃；
(5)可以跟蹤整個程序包；
缺點： 
(1)步驟繁瑣；
(2)無法判斷表被訪問多少次； 
(3)執(zhí)行計劃中謂詞部分不能清晰展現(xiàn)出來；
適用：如果SQL中含函數(shù)，函數(shù)中又套SQL等，即存在多層調(diào)用，想準確分析只能用方法；

方法六:10053

(1)
alter session set tracefile_identifier='10053';
ALTER SESSION SET EVENTS='10053 trace name context forever, level 1';
select count(*) from dba_users;
ALTER SESSION SET EVENTS '10053 trace name context off';

(2)
oradebug  setmypid;
oradebug unlimit;
oradebug event 10053 trace name context forever, level 1;
SELECT ename, dname FROM scott.dept d join scott.emp e USING (deptno);
oradebug  tracefile_name;
Oradebug event 10053 trace name context off;

Example 1:

SYS@orcl> alter session set tracefile_identifier='10053';
SYS@orcl> ALTER SESSION SET EVENTS='10053 trace name context forever, level 1';
SYS@orcl> select count(*) from dba_users;
SYS@orcl> ALTER SESSION SET EVENTS '10053 trace name context off';

[oracle@uf2010813 trace]$ ls -l *10053*
-rw-r-----. 1 oracle oinstall   566260 Aug  1 00:27 orcl_ora_13125_10053.trc
-rw-r-----. 1 oracle oinstall   119517 Aug  1 00:27 orcl_ora_13125_10053.trm

Example 2:

SYS@orcl> oradebug  setmypid;
SYS@orcl> oradebug unlimit;
SYS@orcl> oradebug event 10053 trace name context forever, level 1;
SYS@orcl> SELECT ename, dname FROM scott.dept d join scott.emp e USING (deptno);
SYS@orcl> oradebug  tracefile_name;
/opt/oracle/app/diag/rdbms/orcl/orcl/trace/orcl_ora_11907_10053.trc
SYS@orcl> Oradebug event 10053 trace name context off;

方法七： awrsqrpt.sql 

(1)@?/rdbms/admin/awrsqrpt.sql
Type Specified:  html
Enter value for num_days: 1 
Enter value for begin_snap: 21034
Enter value for end_snap: 21035
Enter value for sql_id: 3ag4uwm6ypra1
Enter value for report_name: awrsqlrpt_0731.html

[oracle@uf2010813 ~]$ ls -l awrsqlrpt_0731.html 
-rw-r--r--. 1 oracle oinstall 13773 Aug  1 03:03 awrsqlrpt_0731.html

---Exec dbms_workload_repository.create_snapshot;

方法八： statistics_level=all 

(1)alter session set statistics_level=all;
(2)執(zhí)行SQL;
(3)查看執(zhí)行計劃；
select * from table(dbms_xplan.display_cursor(null,null,'allstats last'));

Example:

SYS@orcl>show parameter statistics_level
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
statistics_level                     string      TYPICAL

SYS@orcl> alter session set statistics_level=all;

SYS@orcl> set linesize 130
SYS@orcl>  SELECT /* TOTO */ ename, dname FROM scott.dept d join scott.emp e USING (deptno);
SYS@orcl> select * from table(dbms_xplan.display_cursor(null,null,'allstats last'));

PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------------------
SQL_ID  72zuupmcd922s, child number 0
-------------------------------------
 SELECT /* TOTO */  ename, dname   FROM scott.dept d   join scott.emp e
 USING (deptno)

Plan hash value: 844388907

-----------------------------------------------------------------------------------------------------------------------------
| Id  | Operation                    | Name    | Starts | E-Rows | A-Rows |   A-Time   | Buffers |  OMem |  1Mem | Used-Mem |
-----------------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |         |      1 |        |     14 |00:00:00.01 |       7 |       |       |          |

PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------------------
|   1 |  MERGE JOIN                  |         |      1 |     14 |     14 |00:00:00.01 |       7 |       |       |          |
|   2 |   TABLE ACCESS BY INDEX ROWID| DEPT    |      1 |      4 |      4 |00:00:00.01 |       4 |       |       |          |
|   3 |    INDEX FULL SCAN           | PK_DEPT |      1 |      4 |      4 |00:00:00.01 |       2 |       |       |          |
|*  4 |   SORT JOIN                  |         |      4 |     14 |     14 |00:00:00.01 |       3 |  2048 |  2048 | 2048  (0)|
|   5 |    TABLE ACCESS FULL         | EMP     |      1 |     14 |     14 |00:00:00.01 |       3 |       |       |          |
-----------------------------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   4 - access("D"."DEPTNO"="E"."DEPTNO")

PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------------------
       filter("D"."DEPTNO"="E"."DEPTNO")24 rows selected.參考至:《循規(guī)蹈矩：快速讀懂SQL執(zhí)行計劃的套路與工具》---梁敬彬
更多信息見官方文檔：
http://docs.oracle.com/cd/E11882_01/appdev.112/e40758/d_xplan.htm#ARPLS378

DBMS_XPLAN

The DBMS_XPLAN package provides an easy way to display the output of the EXPLAIN PLAN command in several, predefined formats. You can also use the DBMS_XPLAN package to display the plan of a statement stored in the Automatic Workload Repository (AWR) or stored in a SQL tuning set. It further provides a way to display the SQL execution plan and SQL execution runtime statistics for cached SQL cursors based on the information stored in the V$SQL_PLAN and V$SQL_PLAN_STATISTICS_ALL fixed views. Finally, it displays plans from a SQL plan baseline.

Overview
The DBMS_XPLAN package supplies five table functions:
DISPLAY- to format and display the contents of a plan table.
DISPLAY_AWR- to format and display the contents of the execution plan of a stored SQL statement in the AWR.
DISPLAY_CURSOR- to format and display the contents of the execution plan of any loaded cursor.
DISPLAY_SQL_PLAN_BASELINE- to display one or more execution plans for the SQL statement identified by SQL handle
DISPLAY_SQLSET- to format and display the contents of the execution plan of statements stored in a SQL tuning set.

http://docs.oracle.com/cd/E11882_01/server.112/e16604/ch_eight.htm#i1037231

Tuning SQL*Plus
SQL*Plus User's Guide and Reference

Statistics
The statistics are recorded by the server when your statement executes and indicate the system resources required to execute your statement. The results include the following statistics.
(1)recursive calls
Number of recursive calls generated at both the user and system level. Oracle Database maintains tables used for internal processing. When Oracle Database needs to make a change to these tables, it internally generates an internal SQL statement, which in turn generates a recursive call.
(2)db block gets
Number of times a CURRENT block was requested.
(3)consistent gets
Number of times a consistent read was requested for a block
(4)physical reads
Total number of data blocks read from disk. This number equals the value of "physical reads direct" plus all reads into buffer cache.
(5)redo size
Total amount of redo generated in bytes
(6)bytes sent through SQL*Net to client
Total number of bytes sent to the client from the foreground processes.
(7)bytes received through SQL*Net from client
Total number of bytes received from the client over Oracle Net.
(8)SQL*Net round-trips to/from client
Total number of Oracle Net messages sent to and received from the client
(9)sorts (memory)
Number of sort operations that were performed completely in memory and did not require any disk writes
(10)sorts (disk)
Number of sort operations that required at least one disk write
(11)rows processed
Number of rows processed during the operationSTATISTICS_LEVEL = { ALL | TYPICAL | BASIC }
STATISTICS_LEVEL specifies the level of collection for database and operating system statistics. The Oracle Database collects these statistics for a variety of purposes, including making self-management decisions.

The default setting of TYPICAL ensures collection of all major statistics required for database self-management functionality and provides best overall performance. The default value should be adequate for most environments.

When the STATISTICS_LEVEL parameter is set to ALL, additional statistics are added to the set of statistics collected with the TYPICAL setting. The additional statistics are timed OS statistics and plan execution statistics.

Setting the STATISTICS_LEVEL parameter to BASIC disables the collection of many of the important statistics required by Oracle Database features and functionality, including:

(1)Automatic Workload Repository (AWR) Snapshots
(2)Automatic Database Diagnostic Monitor (ADDM)
(3)All server-generated alerts
(4)Automatic SGA Memory Management
(5)Automatic optimizer statistics collection
(6)Object level statistics
(7)End to End Application Tracing (V$CLIENT_STATS)
(8)Database time distribution statistics (V$SESS_TIME_MODEL and V$SYS_TIME_MODEL)
(9)Service level statistics
(10)Buffer cache advisory
(11)MTTR advisory
(12)Shared pool sizing advisory
(13)Segment level statistics
(14)PGA Target advisory
(15)Timed statistics
(16)Monitoring of statistics

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