autotrace统计信息解释
SQL> set autotrace traceonly
SQL> set timing on
SQL> select * from employee;
已选择9行。
已用时间: 00: 00: 00.01
执行计划
----------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)|
---------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 9 | 81 | 3 (0)|
| 1 | TABLE ACCESS FULL| EMPLOYEE | 9 | 81 | 3 (0)|
---------------------------------------------------------------------------------------------------
统计信息
----------------------------------------------------------
0 recursive calls
0 db block gets
8 consistent gets
0 physical reads
0 redo size
583 bytes sent via SQL*Net to client
350 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
9 rows processed
recursive calls ：递归调用。一般原因：dictionary cache未命中；动态存储扩展；PL/SQL语句
db block gets ：从buffer cache中读取的block的数量(多为update)
consistent gets： 数据库缓冲区中读取的数据块的个数
physical reads： 从磁盘读取的block的数量
redo size： DML生成的redo的大小
BYTES SENT VIA SQL*NET TO CLIENT：服务器通过SQL*NET向客户端发送的字节数
BYTES RECEIVED VIA SQL*NET FROM CLIENT：客户端向SQL*NET发送的字节数
SQL*NET ROUNDTRIPS TO/FROM CLIENT：服务器与CLIENT通信的次数
sorts (memory) ：在内存执行的排序量
sorts (disk) ：在磁盘上执行的排序量
rows processed ：返回记录数