Overview of the Automatic Database Diagnostic Monitor (ADDM)

Overview of the Automatic Database Diagnostic Monitor

When problems occur with a database, it is important to perform accurate and timely diagnosis of the problem before making any changes. Often a database administrator (DBA) simply looks at the symptoms and immediately starts changing the system to fix those symptoms. However, an accurate diagnosis of the actual problem in the initial stage significantly increases the probability of success in resolving the problem.

With Oracle Database, the statistical data needed for accurate diagnosis of a problem is stored in Automatic Workload Repository (AWR). Automatic Database Diagnostic Monitor (ADDM):

• Analyzes AWR data on a regular basis

• Diagnoses the root causes of performance problems

• Provides recommendations for correcting any problems

• Identifies non-problem areas of the system

Because AWR is a repository of historical performance data, ADDM can analyze performance issues after the event, often saving time and resources in reproducing a problem.

In most cases, ADDM output should be the first place that a DBA looks when notified of a performance problem. ADDM provides the following benefits:

• Automatic performance diagnostic report every hour by default

• Problem diagnosis based on decades of tuning expertise

• Time-based quantification of problem impacts and recommendation benefits

• Identification of root cause, not symptoms

• Recommendations for treating the root causes of problems

• Identification of non-problem areas of the system

• Minimal overhead to the system during the diagnostic process

Tuning is an iterative process, and fixing one problem can cause the bottleneck to shift to another part of the system. Even with the benefit of ADDM analysis, it can take multiple tuning cycles to reach acceptable system performance. ADDM benefits apply beyond production systems; on development and test systems, ADDM can provide an early warning of performance issues.