4 Copyright © 2005, Oracle. All rights reserved. Managing the Oracle Instance.
12 Copyright © 2004, Oracle. All rights reserved. Automatic Management.
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Transcript of 12 Copyright © 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
12-3 Copyright © 2004, Oracle. All rights reserved.
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$EVENT_NAME view
12-4 Copyright © 2004, Oracle. All rights reserved.
V$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
12-6 Copyright © 2004, Oracle. All rights reserved.
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$EVENT_NAME• event#• name• parameter1• parameter2 • parameter3
12-7 Copyright © 2004, Oracle. All rights reserved.
Instance/DatabaseV$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
12-8 Copyright © 2004, Oracle. All rights reserved.
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
12-9 Copyright © 2004, Oracle. All rights reserved.
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.
12-11 Copyright © 2004, Oracle. All rights reserved.
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.
12-12 Copyright © 2004, Oracle. All rights reserved.
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.
12-13 Copyright © 2004, Oracle. All rights reserved.
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
12-14 Copyright © 2004, Oracle. All rights reserved.
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
12-15 Copyright © 2004, Oracle. All rights reserved.
Advisory Framework Overview
ADDM
SQL Tuning Advisor
SQL Access Advisor
Memory
Space
PGA Advisor
SGA
Segment Advisor
Undo Advisor
Buffer CacheAdvisor
Library CacheAdvisor
PGA
12-18 Copyright © 2004, Oracle. All rights reserved.
Typical Advisor Tuning Session
Adjust task parameters.
Acceptresults?
Implementrecommendations.
Yes
No
Perform analysis.
Create an advisor task.
12-20 Copyright © 2004, Oracle. All rights reserved.
Application Tuning Challenges
DBA
ADDM
SQL Tuning Advisor
High-loadSQL
SQL workload
I can doit for you!
How can Itune my
high-loadSQL?
12-21 Copyright © 2004, Oracle. All rights reserved.
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
12-23 Copyright © 2004, Oracle. All rights reserved.
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
12-28 Copyright © 2004, Oracle. All rights reserved.
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
12-30 Copyright © 2004, Oracle. All rights reserved.
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