13 Copyright © 2005, Oracle. All rights reserved. Monitoring and Improving Performance.
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13Copyright © 2005, Oracle. All rights reserved.
Monitoring and Improving Performance
13-2 Copyright © 2005, Oracle. All rights reserved.
Objectives
After completing this lesson, you should be able to do the following:
• Troubleshoot invalid and unusable objects
• Gather optimizer statistics
• View performance metrics
• Deal with performance issues
13-3 Copyright © 2005, Oracle. All rights reserved.
Performance Monitoring
Memory allocation
issues
Memory allocation
issues
Input/outputdevice
contention
Input/outputdevice
contention
Application code
problems
Application code
problems
Resourcecontention
Resourcecontention
Network bottlenecks
Network bottlenecks
?DBA
13-4 Copyright © 2005, Oracle. All rights reserved.
Monitoring Methodologies
• Reactive
• Proactive:– Server-generated alerts– Automatic Database Diagnostic Monitor (ADDM)
13-5 Copyright © 2005, Oracle. All rights reserved.
Database and Instance Metrics
Several performance statistics are available through:
• Data dictionary
• Dynamic performance views
• Optimizer statistics
DBA
13-7 Copyright © 2005, Oracle. All rights reserved.
Data Dictionary Metrics
You can view the status of:
• PL/SQL code objects
• Indexes
13-8 Copyright © 2005, Oracle. All rights reserved.
Invalid and Unusable Objects
• PL/SQL code objects are recompiled.
• Indexes are rebuilt.
13-10 Copyright © 2005, Oracle. All rights reserved.
Optimizer Statistics
Optimizer statistics are:
• Not real time
• Persistent across instance restarts
• Collected automatically
SQL> SELECT COUNT(*) FROM hr.employees;
COUNT(*)
----------
214
SQL> SELECT num_rows FROM dba_tables
2 WHERE owner='HR' AND table_name = 'EMPLOYEES';
NUM_ROWS
----------
107
13-12 Copyright © 2005, Oracle. All rights reserved.
Using the Manage Optimizer Statistics Page
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Manually Gathering Optimizer Statistics
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Dynamic Performance Views
Dynamic Performance views are:
• Real time
• Nonpersistent across instance restarts
SQL> SELECT name, value FROM v$sysstat
2 WHERE name='sorts (memory)' ORDER BY name;
NAME VALUE
--------------- ----------
sorts (memory) 1979183
SQL> /
NAME VALUE
--------------- ----------
sorts (memory) 1979184
13-16 Copyright © 2005, Oracle. All rights reserved.
Viewing Metric Information
1. Use the All Metrics link in the Related Links region.
2. Drill down for in-depth analysis.
13-17 Copyright © 2005, Oracle. All rights reserved.
Reacting to Performance Issues
Use Enterprise Manager to:
• Find key performance issues
• Drill down to the root cause
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Reacting to Performance Issues
Drill down to performance measurements to identify bottlenecks.
• CPU user: A specific update statement
13-19 Copyright © 2005, Oracle. All rights reserved.
Tuning Tips
Considerations:
• There are some general guidelines that serve as a starting point in performance tuning.
• Your situation may not fit the guideline.
• Test any changes under a representative production environment to see the effects.
• There are written volumes and multiday classes dedicated to tuning an Oracle database.
13-20 Copyright © 2005, Oracle. All rights reserved.
Tuning Activities
The three activities in performance management are:
• Performance planning
• Instance tuning
• SQL tuning
13-21 Copyright © 2005, Oracle. All rights reserved.
Performance Planning
• Investment options
• System architecture
• Scalability
• Application design principles
• Workload testing, modeling, and implementation
• Deploying new applications
13-23 Copyright © 2005, Oracle. All rights reserved.
Instance Tuning
• Have well-defined goals.
• Allocate memory to database structures.
• Consider I/O requirements in each part of the database.
• Tune the operating system for optimal performance of the database.
13-24 Copyright © 2005, Oracle. All rights reserved.
Tuning Memory Allocation
Java pool
Databasebuffer cache
Redo log buffer
Shared pool
Large pool
SGA
Fixed SGA
Streams pool
What is the optimal allocation?
SGA_TARGET = 8G
STATISTICS_LEVEL = TYPICAL
13-26 Copyright © 2005, Oracle. All rights reserved.
Memory Tuning: Guidelines
• Try to fit the SGA into physical memory.
• Tune for a high buffer cache hit ratio, with the following caveats:– Even valid and necessary full table scans lower it.– It is possible that unnecessary repeated reads of
the same blocks are artificially raising it.
• Use the Memory Advisor.
13-28 Copyright © 2005, Oracle. All rights reserved.
Memory Tuning Guidelinesfor the Library Cache
• Establish formatting conventions for developers so that SQL statements match in the cache.
• Use bind variables.
• Eliminate unnecessary duplicate SQL.
• Consider using CURSOR_SHARING.
• Use PL/SQL when possible.
• Cache sequence numbers.
• Pin objects in the library cache.
13-30 Copyright © 2005, Oracle. All rights reserved.
Tuning I/O
• Look for hot spots on the disk.
• Ensure that you have right-sized redo log files.
• Consider moving redo logs to separate disks.
• Consider moving archive logs to separate disks.
• Look for a high I/O rate on the TEMP tablespace.
• Reduce contention for high I/O data files by segregating them.
• Consider striping all data across all disks.
• Consider using Automatic Storage Management.
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Tuning SQL
• Using the SQL Tuning Advisor
• Using indexes and clusters
• Using optimizer hints
• Using V$SQL_PLAN and EXPLAIN PLAN
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Tuning Recommendations
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Recommendation Plan
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SQL Statistics
select count(*) from x where object_id < 340
select count(*) from x where object_id < 220
Each statement causes a hard parse.
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Identifying Duplicate SQL
Bind variable candidates
13-38 Copyright © 2005, Oracle. All rights reserved.
Summary
In this lesson, you should have learned how to:
• Troubleshoot invalid and unusable objects
• Gather optimizer statistics
• View performance metrics
• Deal with performance issues
• Describe some basic tuning steps
13-39 Copyright © 2005, Oracle. All rights reserved.
Practice Overview:Monitoring and Improving Performance
This practice covers the following topics:
• Detecting and repairing unusable indexes
• Using EXPLAIN PLAN• Gathering statistics
• Using the Performance page in Enterprise Manager
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