13 Copyright © 2005, Oracle. All rights reserved. Monitoring and Improving Performance.

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


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


Monitoring Methodologies

• Reactive

• Proactive:– Server-generated alerts– Automatic Database Diagnostic Monitor (ADDM)


Database and Instance Metrics

Several performance statistics are available through:

• Data dictionary

• Dynamic performance views

• Optimizer statistics

DBA


Data Dictionary Metrics

You can view the status of:

• PL/SQL code objects

• Indexes


Invalid and Unusable Objects

• PL/SQL code objects are recompiled.

• Indexes are rebuilt.


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


Using the Manage Optimizer Statistics Page


Manually Gathering Optimizer Statistics


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


Viewing Metric Information

1. Use the All Metrics link in the Related Links region.

2. Drill down for in-depth analysis.


Reacting to Performance Issues

Use Enterprise Manager to:

• Find key performance issues

• Drill down to the root cause


Reacting to Performance Issues

Drill down to performance measurements to identify bottlenecks.

• CPU user: A specific update statement


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.


Tuning Activities

The three activities in performance management are:

• Performance planning

• Instance tuning

• SQL tuning


Performance Planning

• Investment options

• System architecture

• Scalability

• Application design principles

• Workload testing, modeling, and implementation

• Deploying new applications


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.


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


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.


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.


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.


Tuning SQL

• Using the SQL Tuning Advisor

• Using indexes and clusters

• Using optimizer hints

• Using V$SQL_PLAN and EXPLAIN PLAN


Tuning Recommendations


Recommendation Plan


SQL Statistics

select count(*) from x where object_id < 340

select count(*) from x where object_id < 220

Each statement causes a hard parse.


Identifying Duplicate SQL

Bind variable candidates


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


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

13 Copyright © 2005, Oracle. All rights reserved. Monitoring and Improving Performance.

Documents

performance slide

oracle database

optimizer statistics

performance statistics

performance tuning

typical slide

notes page slide

memory tuning