Book Image

Oracle Database 11g : Underground Advice for Database Administrators

By : April Sims
Book Image

Oracle Database 11g : Underground Advice for Database Administrators

By: April Sims

Overview of this book

Today DBAs are expected to deploy and manage large databases with quality service and little to no downtime. The DBA's main focus is on increasing productivity and eliminating idle redundancy throughout the enterprise. However, there is no magic set of best practices or hard and fast rules that DBAs need to follow, and this can make life difficult. But if DBAs follow some basic approaches and best practices, tasks can be performed more efficiently and effectively.This survival guide offers previously unwritten underground advice for DBAs. The author provides extensive information to illuminate where you fit in, and runs through many of the tasks that you need to be watchful of, extensively covering solutions to the most common problems encountered by newcomers to the world of Oracle databases.The book will quickly introduce you to your job responsibilities, as well as the skills, and abilities needed to be successful as a DBA. It will show you how to overcome common problems and proactively prevent disasters by implementing distributed grid computing—scalable and robust—with the ability to redeploy or rearchitect when business needs change. Reduce downtime across your enterprise by standardizing hardware, software, tools, utilities, commands, and architectural components.This book will also help you in situations where you need to install Oracle Database 11g or migrate to new hardware making it compliant with a Maximum Availability Architecture. By the end of this book you will have learned a lot and gained confidence in your abilities. You will be armed with knowledge as to which tools are best used to accomplish tasks while proactively moving towards an automated environment.
Table of Contents (14 chapters)
Oracle Database 11g—Underground Advice for Database Administrators
Credits
About the author
About the reviewers
Preface
Index

Bind peeking and Adaptive Cursor Sharing


This section requires some basic knowledge of tuning, as it pertains to bind peeking and Adaptive Cursor Sharing. Before the 10g Version of Oracle Database, there were performance issues related to bind peeking. The query optimizer takes a quick look (peek) at user-defined bind variables the first time they appear in a cursor. A bind variable is a substitution variable instead of a literal—in this example as A: instead of the literal 100. That peek may or may not be the best value to base the execution plan of a query on. The next time the optimizer encounters that same cursor, no more peeking takes place no matter the bind value, because the cursor is shared among all the queries for the same information.

Why wouldn't the first peek be the best one to use? It depends on the mathematical distribution of the data. For example, a table with three column values—1, 10, 100, contains 245 rows, 2 rows and 6 rows of each value respectively. There is a larger...