Oracle Study之--resmgr:cpu quantum等待事件
在AWR Report中出现“resmgr:cpu quantum”等待事件：
“resmgr:cpu quantum”等待事件：
参考metalink的解决方案，是oracle资源管理方面的问题，原文如下：
Symptoms
High waits on event ‘resmgr:cpu quantum‘ might be noticed even when resource manager is disabled. You already have confirmed parameter RESOURCE_MANAGER_PLAN is set to null but still noticing the above wait events.
Top 5 Timed Foreground Events:
Event Waits Time(s) Avg wait(ms) % DB time Wait Class ------------------------ ------- -------- ------------ -------------- ---------- ----------- resmgr:cpu quantum 1,596 346,281 216968 89.19 Scheduler db file scattered read 171,071 14,778 86 3.81 User I/O log file sync 28,575 10,810 378 2.78 Commit db file sequential read 943,457 6,569 7 1.69 User I/O DB CPU 2,133 0.55
Cause
This could be due to DEFAULT_MAINTENANCE_PLAN. From 11g onwards every weekday window has a pre-defined Resource Plan called DEFAULT_MAINTENANCE_PLAN, which will become active once the related window opens.
Following entries can also be noted in alert log at the time of issue.
Wed Sep 16 02:00:00 2009
Clearing Resource Manager plan via parameter：
Wed Sep 16 22:00:00 2009
Setting Resource Manager plan SCHEDULER[0x2C55]:DEFAULT_MAINTENANCE_PLAN via scheduler window
Setting Resource Manager plan DEFAULT_MAINTENANCE_PLAN via parameter
Wed Sep 16 22:00:05 2009
Begin automatic SQL Tuning Advisor run for special tuning task "SYS_AUTO_SQL_TUNING_TASK"
Solution
To disable the DEFAULT_MAINTENANCE_PLAN you can use the below steps as suggested inNote 786346.1
1. Set the current resource manager plan to null (or another plan that is not restrictive):
alter system set resource_manager_plan=‘‘;
2. Change the active windows to use the null resource manager plan (or other nonrestrictive plan)
using:3. Then, for each window_name (WINDOW_NAME from DBA_SCHEDULER_WINDOWS), run:
execute dbms_scheduler.set_attribute(‘WEEKNIGHT_WINDOW‘,‘RESOURCE_PLAN‘,‘‘); execute dbms_scheduler.set_attribute(‘WEEKEND_WINDOW‘,‘RESOURCE_PLAN‘,‘‘);
3. Then, for each window_name (WINDOW_NAME from DBA_SCHEDULER_WINDOWS), run:
execute dbms_scheduler.set_attribute(‘<window name>‘,‘RESOURCE_PLAN‘,‘‘);
execute dbms_scheduler.set_attribute(‘<window name>‘,‘RESOURCE_PLAN‘,‘‘);
References
NOTE:392037.1 - Database Hangs. Sessions wait for ‘resmgr:cpu quantum‘
NOTE:756734.1 - 11g: Scheduler Maintenance Tasks or Autotasks
NOTE:786346.1 - Resource Manager and Sql Tunning Advisory DEFAULT_MAINTENANCE_PLAN
NOTE:806893.1 - Large Waits With The Wait Event "Resmgr:Cpu Quantum"
注意：
但是很多用户会发现禁用资源计划很多时候没有作用.可以禁用Oracle缺省启用的资源调度,最后通过以下参数设置解决问题:
_resource_manager_always_on = false