Less13 Performance Tb

8/14/2019 Less13 Performance Tb

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13Copyright 2005, Oracle. All rights reserved.

Monitoring and Improving Performance


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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


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Monitoring Methodologies

Reactive

Proactive:

Server-generated alerts

Automatic Database Diagnostic Monitor (ADDM)


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Database and Instance Metrics

Several performance statistics are available through:

Data dictionary

Dynamic performance views

Optimizer statistics

DBA


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Database and Instance Metrics

Full Notes Page


7/4013-7 Copyright 2005, Oracle. All rights reserved.

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.



Invalid and Unusable Objects

Full Notes Page



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_tables2WHERE owner='HR'ANDtable_name='EMPLOYEES';

NUM_ROWS

----------

107



Optimizer Statistics

Full Notes Page



Using the Manage Optimizer

Statistics Page



Manage Optimizer Statistics Page

Full Notes 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



Performance Planning

Full Notes Page



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

Database

buffer cache

Redo log

buffer

Shared pool

Large pool

SGA

Fixed SGA

Streams pool

What is the optimal allocation?

SGA_TARGET = 8G

STATISTICS_LEVEL = TYPICAL



Tuning Memory Allocation

Full Notes Page


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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.


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Memory Tuning Guidelines

Full Notes Page


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for 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.


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for the Library Cache

Full Notes Page


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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 I/O

Full Notes Page


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Tuning SQL

Using the SQL Tuning Advisor

Using indexes and clusters

Using optimizer hints

UsingV$SQL_PLAN and EXPLAINPLAN


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Tuning SQL

Full Notes Page


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Tuning Recommendations


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Recommendation Plan


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SQL Statistics

select count(*) fromxwhere object_id < 340

select count(*) fromxwhere object_id < 220

Each statement causes a hard parse.


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Identifying Duplicate SQL

Bind variable

candidates


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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


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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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Full Notes Page

Less13 Performance Tb

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