OCP-1Z0-053-V12.02-82题

coverl

82.Identify the three predefined server-generated alerts. (Choose three.)
A. Drop User
B. Tablespace Space Usage
C. Resumable Session Suspended
D. Recovery Area Low On Free Space
E. SYSTEM Tablespace Size Increment
Answer: BCD
答案解析：
参考：http://blog.iyunv.com/rlhua/article/details/12683525
官方参考：http://docs.oracle.com/cd/E11882_01/server.112/e25494/monitoring.htm#ADMIN11247





预警是当数据库处于不理想状态且需要引起注意时发出的通知。默认情况下，Oracle DB通过Enterprise Manager Database Control 提供预警。也可选择配置Enterprise Manager 以向管理员发送有关问题状况的电子邮件，还可在控制台上显示预警信息。另外，还可为系统的多个相关度量设置阈值。如果数据库偏离正常读数太多而达到了这些阈值，Oracle Database 11g会预先发送通知。提前通知潜在的问题，可使用户迅速作出响应，并通常在用户注意到这些问题之前就解决这些问题。默认情况下受监视的度量大约有60 个，其中包括：· 中断作业计数· 等待所用的数据库时间百分比(%)· 转储区占用率(%)· 参照基线的SQL 响应时间百分比(%)· 表空间占用率(%)· 一般意外事件 另外一些可提前提供问题通知的重要度量有：· 平均文件读取时间（厘秒）· 响应时间（每事务处理）· 等待时间(%)
Monitoring Database Operations with Server-Generated Alerts
　　
　　
Aserver-generated alert is a notification from the Oracle Database server of an impending problem. The notification may contain suggestions for correcting the problem. Notifications are also provided when the problem condition has been cleared.
Alerts are automatically generated when a problem occurs or when data does not match expected values for metrics, such as the following:

• 　　Physical Reads Per Second
  
• 　　User Commits Per Second
  
• 　　SQL Service Response Time
  

　　Server-generated alerts can be based on threshold levels or can issue simply because an event has occurred. Threshold-based alerts can be triggered at both threshold warning and critical levels. The value of these levels can becustomer-defined or internal values, and some alerts have default threshold levels which you can change if appropriate. For example, by default a server-generated alert is generated for tablespace space usage whenthe percentage of space usage exceeds either the 85% warning or 97% critical threshold level. Examples of alerts not based on threshold levels are:

• 　　Snapshot Too Old
  
• 　　Resumable Session Suspended
  
• 　　Recovery Area Space Usage
  

An alert message is sent to the predefined persistent queue ALERT_QUE owned by the user SYS. Oracle Enterprise Manager reads this queue and provides notifications about outstanding server alerts, andsometimes suggests actions for correcting the problem. The alerts are displayed on the Enterprise Manager Database Home page and can be configured to send email or pager notifications to selected administrators. If an alert cannot be written to the alert queue,a message about the alert is written to the Oracle Database alert log.
Background processes periodically flush the data to the Automatic Workload Repository to capture a history of metric values. The alert history table andALERT_QUE are purged automatically by the system at regular intervals.

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