12 copyright © 2004, oracle. all rights reserved. automatic management

12Copyright © 2004, Oracle. All rights reserved.

Automatic Management

12-2 Copyright © 2004, Oracle. All rights reserved.

Objectives

After completing this lesson, you should be able to:

• Describe the various tools used to diagnose database performance issues

• Access the database advisors

• Use the SQL Tuning Advisor to improve database performance


Oracle Wait Events

• A collection of wait events provides informationon the sessions or processes that had to wait or must wait for different reasons.

• These events are listed in the V$EVENT_NAME view


V$SGASTAT• pool• name• bytes

V$SYSSTAT• statistic# • name• class• value• stat_id

V$SYSTEM_EVENT• event• total_waits• total_timeouts• time_waited• average_wait• time_waited_micro

System Statistics

V$EVENT_NAME• event_number• event_id• name• parameter1 • parameter2 • parameter3• wait_class

V$SYSTEM_WAIT_CLASS• wait_class_id • wait_class#• wait_class• total_waits• time_waited


Displaying Session-Related Statistics

V$STATNAME• statistic# • name • class

V$SESSTAT• sid• statistic#• value

V$SESSION• sid• serial#• username• command• osuser• seq#• event#• event• p1/2/3text• p1/2/3• p1/2/3raw• wait_class• wait_time• seconds_in_wait• state• ...

V$SESSION_EVENT• sid• event• total_waits• total_timeouts• time_waited• average_wait• max_wait• time_waited_micro• event_id

V$EVENT_NAME• event#• name• parameter1• parameter2 • parameter3


Instance/DatabaseV$DATABASEV$INSTANCEV$PARAMETERV$SPPARAMETERV$SYSTEM_PARAMETERV$PROCESSV$BGPROCESSV$PX_PROCESS_SYSSTAT

V$SYSTEM_EVENT

Troubleshooting and Tuning Views

DiskV$DATAFILEV$FILESTATV$LOGV$LOG_HISTORYV$DBFILEV$TEMPFILEV$TEMPSEG_USAGEV$SEGMENT_STATISTICS

ContentionV$LOCKV$UNDOSTATV$WAITSTATV$LATCH

MemoryV$BUFFER_POOL_STATISTICSV$LIBRARYCACHEV$SGAINFOV$PGASTAT


Statistics Collection

• There are different types of statistics:– Optimizer statistics– System statistics

• There are different methods of collecting statistics:– Automatically through GATHER_STATS_JOB– Manually with the DBMS_STATS package– By setting database initialization parameters– Importing statistics from another database


Automatic Optimizer Statistics Collection: Overview

• Oracle8i Database provides DBMS_STATS package:– DBA determines how to gather statistics.– DBA determines when to gather statistics.

• Oracle9i Database determines how to gather statistics:– Statistics can be gathered using a single command.– DBA determines when to gather statistics.

• Oracle Database 10g fully automates statistics gathering:– DBA no longer needs to gather statistics.– Table monitoring is used by default.


Dictionary and Special Views

• The following dictionary and special views provide useful statistics after using the DBMS_STATS package:– DBA_TABLES, DBA_TAB_COLUMNS– DBA_CLUSTERS– DBA_INDEXES, INDEX_STATS– INDEX_HISTOGRAM, DBA_TAB_HISTOGRAMS

• This statistical information is static until you reexecute the appropriate procedures in DBMS_STATS.


Statspack

• Execute statspack.snap to collect statistics.

• Automate the collection of statistics using the spauto.sql script.

• Produce a report using the spreport.sql script.

• Set TIMED_STATISTICS to TRUE to collect timing information.


Workload Repository

SYSAUX

SGA

In-memorystatistics

6:00 a.m.7:00 a.m.

8:00 a.m.

Snapshot 1Snapshot 2Snapshot 3

Snapshot 49:00 a.m.

9:30 a.m.

ADDM finds top problemsMMON


AWR Snapshot Baselines

DBMS_WORKLOAD_REPOSITORY.CREATE_BASELINE ( - start_snap_id IN NUMBER , end_snap_id IN NUMBER , baseline_name IN VARCHAR2);

Relevant periodin the past


Advisory Framework Overview

ADDM

SQL Tuning Advisor

SQL Access Advisor

Memory

Space

PGA Advisor

SGA

Segment Advisor

Undo Advisor

Buffer CacheAdvisor

Library CacheAdvisor

PGA


Database Control and Advisors


Typical Advisor Tuning Session

Adjust task parameters.

Acceptresults?

Implementrecommendations.

Yes

No

Perform analysis.

Create an advisor task.


Manually Invoking ADDM


Application Tuning Challenges

DBA

ADDM

SQL Tuning Advisor

High-loadSQL

SQL workload

I can doit for you!

How can Itune my

high-loadSQL?


SQL Tuning Advisor Overview

Add Missing Index

Run Access Advisor

Restructure SQL

Plan Tuning

(SQL Profile)

Automatic Tuning Optimizer

SQL AnalysisOptimization Mode

Access Analysis Optimization Mode

Plan Tuning Optimization Mode

Statistics CheckOptimization Mode Detect Stale/Missing

Statistics

Comprehensive SQL Tuning

SQL Tuning Advisor


SQL Tuning Advisor Options and Recommendations


Using the SQL Tuning Advisor

• Use the SQL Tuning Advisor to analyze SQL statements and obtain performance recommendations.

• Sources for SQL Tuning Advisor to analyze:– Top SQL: Analyzes the top SQL statements

currently active– SQL Tuning Sets: Analyzes a set of SQL statements

you provide– Snapshots: Analyzes a snapshot– Baselines: Analyzes a baseline


Using the SQL Tuning Advisor: Example


Using the SQL Access Advisor


The Undo Management Page


Automatic Undo Retention Tuning

• Proactive tuning:– Undo retention is tuned for longest-running query.– Query duration information is collected every 30

seconds.

• Reactive tuning:– Undo retention is gradually lowered under space

pressure.– Oldest unexpired extents are used first.– Undo retention never goes below either

UNDO_RETENTION or 15 minutes (whichever is less).

• Enabled by default


The Undo Advisor Page


Summary

In this lesson, you should have learned how to:

• Describe the various tools used to diagnose database performance issues

• Access the database advisors

• Use the SQL Tuning Advisor to improve database performance


Practice 12 Overview:Optimizing Database Performance

This practice covers proactively tuning your database using ADDM.

12 copyright © 2004, oracle. all rights reserved. automatic management

Documents

sysstat v

value v

statistics contention

datafile v

lock v

tempfile v

waitstat v

undostat v