oracle db file sequential read,对比发现db file sequential read等待事件加大

System altered

SQL>select event,total_waits,time_waited,average_wait from

v$session_eventwhere sid=1 order by

total_waits desc;

EVENTTOTAL_WAITS TIME_WAITED AVERAGE_WAIT

----------------------------------------------------------------

----------- ----------- ------------

db file sequential read139990.71--此等待事件增大，是因为会读取与本话相关的一些字典表的数据

SQL*Net message to client2400

SQL*Net message from client2326060811330.78

log file sync500.09

Disk file operations I/O400.06

events in waitclass Other361.93

SQL*Net break/reset to client200.01

enq: RO - fast object reuse110.81

8 rows selected

---读取表记录

SQL> select * from t_single;

A

----------

1

2

---对比发现db file sequential read等待事件加大了

SQL> /

EVENTTOTAL_WAITS TIME_WAITED AVERAGE_WAIT

----------------------------------------------------------------

----------- ----------- ------------

db file sequential read1421040.73

SQL*Net message to client2600

SQL*Net message from client2526376310550.52

log file sync500.09

Disk file operations I/O400.06

events in waitclass Other361.93

SQL*Net break/reset to client200.01

enq: RO - fast object reuse110.81

8 rows selected

---表已在buffer cache中

SQL> /

A

----------

1

2

---对比发现如表已在buffer cache则db file sequential read不会增加

SQL> /

EVENTTOTAL_WAITS TIME_WAITED

AVERAGE_WAIT

----------------------------------------------------------------

----------- ----------- ------------

db file sequential read1421040.73

SQL*Net message to client2800

SQL*Net message from client2728038410384.58

log file sync500.09

Disk file operations I/O400.06

events in waitclass Other361.93

SQL*Net break/reset to client200.01

enq: RO - fast object reuse110.81

8 rows selected unix培训