12C-OCP升级1z-060-015

In your multitenant container database (CDB) containing pluggable databases (PDB), users

complain about performance degradation.

How does real-time Automatic database Diagnostic Monitor (ADDM) check performance

degradation and provide solutions?

A. It collects data from SGA and compares it with a preserved snapshot.

B. It collects data from SGA, analyzes it, and provides a report.

C. It collects data from SGA and compares it with the latest snapshot.

D. It collects data from both SGA and PGA, analyzes it, and provides a report.

 
正确答案：B

12C ADDM官方文档的位置
http://docs.oracle.com/database/121/TGDBA/pfgrf_diag.htm#TGDBA94241

答案解析：

Real-Time ADDM Analysis

Introduced in Oracle Enterprise Manager Cloud Control 12c, Real-Time ADDM helps you to analyze and resolve problems in unresponsive or hung databases that traditionally require you to restart the database. Real-Time ADDM runs through a set of predefined criteria
to analyze the current performance of the database. After analyzing the problem, Real-Time ADDM helps you to resolve the identified issues—such as deadlocks, hangs, shared pool connections, and other exception situations—without having to restart the database.

Real-Time ADDM Triggers

Starting with Oracle Database 12c, Real-Time ADDM proactively detects transient database performance issues. To do this, Real-Time ADDM runs automatically every 3 seconds and uses in-memory data to diagnose any performance spikes in the database.

Real-Time ADDM triggers an analysis automatically when a performance problem is detected, as described in the following steps:
1.Every 3 seconds, the manageability monitor process (MMON) performs an action to obtain performance statistics without lock or latch.

2.The MMON process checks these statistics and triggers a Real-Time ADDM analysis if any of the issues listed in Table 7-1 are detected.

3.The MMON slave process creates the report and stores it in the AWR.

4.To view metadata for the report, use the DBA_HIST_REPORTS view.
默认启动real time ADDM的条件

14:32:43 sys@kiwi> show parameter CONTROL_MANAGEMENT_PACK_ACCESS

NAME                                 TYPE        VALUE

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

control_management_pack_access       string      DIAGNOSTIC+TUNING

14:32:51 sys@kiwi> show parameter level

NAME                                 TYPE        VALUE

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

audit_syslog_level                   string

parallel_degree_level                integer     100

plsql_optimize_level                 integer     2

statistics_level                     string      TYPICAL
手动的启动real time ADDM的方式

Let us assume a scenario that your database is in “hanging” state:

sqlplus ‘/ as sysdba’  (if you can’t access then use: sqlplus -prelim “/as sysdba”)

SQL>@$ORACLE_HOME/rdbms/admin/rtaddmrpt.sql

SQL>exit

Now you have successfully generated a Real-Time ADDM, check it and see what is causing the problem (the file will be in HTML format).