Oracle Table Statistics Importance and Benefits for Performance Tuning

YouTube video

Introduction

Welcome to RK SoftAcademy, your go-to channel for comprehensive tutorials on Oracle and Unix technologies. In this video, we will address an important question raised by one of our viewers, Siddharth, regarding the significance of gathering statistics in Oracle. We will delve into the topic of Oracle table statistics and explore why it is crucial for optimizing performance in Oracle databases.

About RK SoftAcademy

Before we jump into the topic, let us quickly introduce ourselves. RK SoftAcademy is a platform where you can find in-depth training on various Oracle technologies. As a senior Oracle consultant, technical and corporate trainer, and interviewer with over 17 years of experience, we aim to share our expertise and knowledge with job seekers, students, and anyone interested in Oracle and database platforms.

The Need for Gathering Table Statistics

Now, let’s address Siddharth’s question and delve into the importance of gathering table statistics in Oracle databases. Statistics, in this context, refer to the information about the tables in the database. When performing operations such as updating, deleting, or inserting records in a table with a large amount of data, Oracle executes SQL statements in multiple steps.

To gain a deeper understanding of this process, we recommend watching our video on “Select Query Processing in Oracle.” This video provides a detailed explanation of how select queries are processed within the Oracle database and can help you comprehend the execution of SQL statements.

Role of Oracle Optimizer and Explain Plan

Oracle relies on the Oracle optimizer to choose the most efficient execution plan for a SQL statement. The optimizer generates multiple execution plans or explain plans and selects the one with the lowest cost. This is where table statistics play a vital role. Oracle statistics, or table statistics, assist the optimizer in selecting the best execution plan for a SQL statement.

Gathering Table Statistics Using DBMS_STATS Package

To gather table statistics, we can utilize the default package in Oracle called DBMS_STATS. This package provides the necessary procedures to collect statistics for tables. Let’s take a practical example to understand the process better.

Consider a table named “Gross Domestic Product One” with various attributes like period, data value, unit, magnitude, subject, serial, and status. This table contains a significant number of records. When querying this table, Oracle executes a full table scan to access the necessary data.

Updating and Analyzing Explain Plan

To showcase the impact of statistics on the execution plan, we will update the status column and observe the changes in the explain plan. By reversing the status values and recreating the necessary index, we can simulate a scenario where statistics need to be gathered.

Once the statistics are gathered using the DBMS_STATS package and the necessary parameters, we can generate an explain plan for the modified SQL statement. The explain plan reveals that the optimizer now performs a full table scan instead of accessing the rows one by one.

Conclusion

Gathering table statistics in Oracle holds immense significance for optimizing performance. By providing vital information about the tables, statistics assist the optimizer in choosing the most efficient execution plan for SQL statements. This, in turn, enhances the overall performance of Oracle databases.

We hope this article has shed light on the importance of gathering table statistics in Oracle and how it contributes to performance tuning. Remember to watch our previous tutorials to further expand your knowledge of Oracle and its advanced topics. Stay tuned for more informative videos and tutorials on RK SoftAcademy!

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