oracle之数据字典屣履造门(二)
s statement
SYS@orcl#set autotrace on statistices;
SP2-0735: 未知的 SET 选项开头 "statistice..."
SYS@orcl#set autotrace on statistics;
SYS@orcl#select * from t2;
EMPNO ENAME
---------- --------------------
7521 WARD
统计信息
----------------------------------------------------------
0 recursive calls
0 db block gets
3 consistent gets
0 physical reads
0 redo size
600 bytes sent via SQL*Net to client
524 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
SYS@orcl#select * from t2;
EMPNO ENAME
---------- --------------------
7521 WARD
执行计划
----------------------------------------------------------
Plan hash value: 1513984157
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 20 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS FULL| T2 | 1 | 20 | 2 (0)| 00:00:01 |
--------------------------------------------------------------------------
Note
-----
- dynamic sampling used for this statement
统计信息
----------------------------------------------------------
0 recursive calls
0 db block gets
3 consistent gets
0 physical reads
0 redo size
600 bytes sent via SQL*Net to client
524 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
SYS@orcl#
SYS@orcl#set autotrace traceonly;
SYS@orcl#select * from t;
执行计划
----------------------------------------------------------
Plan hash value: 1601196873
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 5 | 180 | 3 (0)| 00:00:01 |
| 1 | TABLE ACCESS FULL| T | 5 | 180 | 3 (0)| 00:00:01 |
--------------------------------------------------------------------------
统计信息
----------------------------------------------------------
0 recursive calls
0 db block gets
4 consistent gets
0 physical reads
0 redo size
1184 bytes sent via SQL*Net to client
524 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
5 rows processed
总结：该工具可以查看语句的统计信息可以变化命令使用非常灵活，
SYS@orcl#set autotrace
用法: SET AUTOT[RACE] {OFF | ON | TRACE[ONLY]} [EXP[LAIN]] [STAT[ISTICS]]
便于语句调优。在此记录加深一下印象。呵呵，原来这个工具还有多种花样。
X$kvit 内部表：英文名字叫：kernel layer performance layer information tables transitory instance parameters；
#select kvitval,kvittag,kvitdsc from x$kvit
2 ;
KVITVAL KVITTAG KVITDSC
---------- -------------------- --------------------------------------------------------------------------------
1 ksbcpu