2 copyright © 2006, oracle. all rights reserved. performance tuning: overview

2Copyright © 2006, Oracle. All rights reserved.

Performance Tuning: Overview

2-2 Copyright © 2006, Oracle. All rights reserved.

Objectives

After completing this lesson, you should be able to do the following:

• Write appropriate tuning goals

• Apply the tuning methodology

• Balance performance and safety trade-offs

• Identify common tuning problems

• Log a performance Service Request with Oracle Support


General Tuning Session

Tuning sessions have the same procedure:

1. Define the problem and state the goal.

2. Collect current statistics.

3. Consider some common performance errors.

4. Build a trial solution.

5. Implement and measure the change.

6. Decide: “Did the solution meet the goal?”– No? Then go to step 3 and repeat.– Yes? Then create a new baseline.


Defining the Problem

To discover and define the problem:

• Listen to user feedback

• Check the alert log and trace files for errors

• Check the parameter file for any diagnostic or inappropriate parameter setting

• Check memory, I/O, and CPU usage. Identify processes with resource usage anomalies

• Identify and tune SQL statements that are heavy consumers of CPU or I/O

• Collect instance and operating system (OS) statistics


Setting the Priority

Choose the problem that has the greatest impact:

• Analyze system performance in terms of work done (CPU or service time) versus time spent waiting for work (wait time).DB 타임 감소가 목표

• Determine which component consumes the greatest amount of time.

• Drill down to tune that component, if appropriate.


Tuning Methodology:Setting the Priority Example

Time Model System Stats DB/Inst: ORCL Snaps: 1-11-> Ordered by % of DB time desc, Statistic name

Statistic Time (s) % of DB time--------------------------- --------- ---------sql execute elapsed time 467.0 77.1DB CPU 414.2 68.4parse time elapsed 200.5 33.1hard parse elapsed time 109.0 18.0…DB time 605.8


Common Tuning Problems

The most common tuning problems:

• SQL statements

• Session management

• Shared pool sizing and contention

• Buffer cache sizing and contention

• Data block contention

• Redo log and redo buffer tuning

• Undo tuning

• I/O issues

• Locking issues


ADDM Tuning Session

ADDM tuning session has the same procedure as the general tuning session, but combines steps:

1. View the ADDM report.A. Collect current statistics; compare with previous set.

B. Compare to performance issues knowledge base.

C. Define the problem and make recommendations.

2. Review recommendations.D. Build a trial solution.

3. Implement the recommendation.E. Implement and measure the change.

4. Review the next ADDM report.F. Decide: “Did the solution meet the goal?”


Effective Tuning Goals

Effective tuning goals are:

• Specific

• Measurable

• Achievable


Tuning Objectives

The objectives of tuning are:

• Minimizing response time

• Increasing throughput

• Increasing load capabilities

• Decreasing recovery time


DB Time

DB Time =

DB Wait Time +

DB CPU Time


CPU and Wait Time Tuning Dimensions

Scalableapplication

Possiblyneeds SQL

tuning

Needsinstance/RAC

tuning

CPUtime

Waittime

No gain achievedby adding

CPUs/nodes

DB time = DB CPU time + DB wait time


Tuning Life Cycle Phases

Application life cycle can be divided into different phases:

• Application design and development

• Testing: Database configuration

• Deployment: Adding a new application to an existing database

• Production: Troubleshooting and tuning


Tuning Steps During Life Cycle

1. Tune the design.

2. Tune the application.

3. Tune memory.

4. Tune I/O.

5. Tune contention.

6. Tune the operating system.


Application Design and Development

The application can be tuned even in the design and development phases by building and tuning test cases.

• Check normalization against major functions.

• Check data structures against access times.

• Look at points where processes are serialized.

• Tune the major reports.

• Tune the high-volume processes.


Testing: Database Configuration

The testing phase allows tuning at a deeper level:

• Check physical layout.

• Monitor for resource contention.– Memory utilization– Locks– Disk hot spots

• Test for resource exhaustion.


Deployment

Deployment of:

• New application and database – Take baseline. – Monitor growth and performance.

• New application in existing database– Take baseline before deployment.– Take baseline after deployment. – Compare baselines.


Production

Tuning is reactive. You need to know:

What has changed?

Where is the baseline?


Collecting a Baseline Set of Statistics

A baseline set of statistics is used to:

• Provide a set of statistics that are collected when the system is operating within the bounds set

• Compare the baseline statistics with current statistics

• Create a hypothesis about what has changed onthe system


Performance Versus Safety Trade-Offs( 반비례 )

Factors that affect performance:

• Multiple control files

• Multiple redo log members in a group

• Frequent checkpointing

• Backing up data files

• Performing archiving

• Block check sums

• Number of concurrent users and transactions


Filing a Performance Service Request

File a Performance Service Request:

• Is the problem instancewide or query specific?

• Identify the root cause.

• Provide Statspack or AWR reports, and OS statistics.

• Provide Remote Diagnostics Agent (RDA) reports.

• Provide SQL_TRACE reports.


RDA Report


Monitoring and Tuning Tool: Overview

Alert logTrace files

Performance views

Optimizer statisticsSQL statisticsBase statistics

HistogramsMetrics

Service statisticsASH

tkproftrcsess

System statisticsSession statistics

Wait modelTime model

Alerts

ASH reports

Services


Monitoring and Tuning Tool: Overview

Statspack

AWR

EM performance pages

Metric baselineEM policies

ADDMAdvisors

Direct SGA monitorHang analyzer

Baselines

AWR baselines

Compare periods

Services


Practice Overview: Write Tuning Goals

This practice covers the following topics:

• Transform a problem definition into a goal

• Make a goal measurable


Summary

In this lesson, you should have learned how to:

• Write appropriate tuning goals

• Identify the proper methodology for tuning in different development phases

• Balance performance and safety trade-offs

• Identify common tuning problems

• Log a performance Service Request with Oracle Support

2 copyright © 2006, oracle. all rights reserved. performance tuning: overview

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