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本帖最后由 wei-xh 于 2013-8-6 15:22 编辑
开心的DBA 发表于 2013-8-6 14:08
GOOD JOB!还没有细看,问个问题,文章的开头提到:
SEQ的NOCACHE属性会导致LOG FILE SYNC?
楼主可否给出 ...
很容易证明:
execute snap_system_events.start_snap
select seq_wxh.nextval from dual;
select seq_wxh.nextval from dual;
select seq_wxh.nextval from dual;
select seq_wxh.nextval from dual;
select seq_wxh.nextval from dual;
execute snap_system_events.end_snap
---------------------------------
System Waits:- 06-Aug 11:10:49
Interval:- 0 seconds
---------------------------------
Event Waits Time_outs Csec Avg Csec Max Csec
----- ----- --------- ---- -------- --------
rdbms ipc message 6 1 170 28.333 0
class slave wait 0 0 81 81.000 0
control file sequential read 4 0 0 .000 0
control file parallel write 1 0 0 .000 0
log file parallel write 5 0 1 .200 0
log file sync 5 0 1 .200 0
SQL*Net message to client 17 0 0 .000 0
SQL*Net message from client 17 0 5 .294 0
我们一共调用了五次seq,查看快照期间的系统等待事件信息,可要看到log file sync,log file parallel write都分别有5次。(测试的SEQ为nocache)
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