Book Image

Teradata Cookbook

By : Abhinav Khandelwal, Viswanath Kasi, Rajsekhar Bhamidipati
Book Image

Teradata Cookbook

By: Abhinav Khandelwal, Viswanath Kasi, Rajsekhar Bhamidipati

Overview of this book

Teradata is an enterprise software company that develops and sells its eponymous relational database management system (RDBMS), which is considered to be a leading data warehousing solutions and provides data management solutions for analytics. This book will help you get all the practical information you need for the creation and implementation of your data warehousing solution using Teradata. The book begins with recipes on quickly setting up a development environment so you can work with different types of data structuring and manipulation function. You will tackle all problems related to efficient querying, stored procedure searching, and navigation techniques. Additionally, you’ll master various administrative tasks such as user and security management, workload management, high availability, performance tuning, and monitoring. This book is designed to take you through the best practices of performing the real daily tasks of a Teradata DBA, and will help you tackle any problem you might encounter in the process.
Table of Contents (19 chapters)
Title Page
Dedication
Packt Upsell
Contributors
Preface
Index

Resolving skew in database


A database can run out of space if it has excessive tables that are skewed. Skew in small tables is understandable and can't be controlled, whereas skew in big tables can be controlled and reduced.

Note

DBC.TableSizeProvides space by AMP about table space usage for each AMP.

Getting ready

We will connect to our Teradata database instance and open SLQA to generate the list of tables with their space and skew details.

How to do it...

  1. Pick the database on which you need to analyze the skew tables.
  2. Execute this query to get the list of tables:
/**Skew table in a database query**/
Lock Dbc.TableSize For Access 
Lock Dbc.tables For Access 
SELECT B.databasename , B.TableName , A.LastAccessTimeStAMP , SUM ( currentperm ) ( NAMED CurrentPerm ) ,
 MAXIMUM ( currentperm ) ( NAMED MaxPerm ) , AVG ( currentperm ) ( NAMED AvgPerm ) ,
 ( ( MAXIMUM ( currentperm ) - AVG ( currentperm ) ) * 100.0 ) / ( MAXIMUM ( currentperm ) ) ( NAMED SkewPercent ) 
FROM dbc.tablesize B INNER JOIN...