Book Image

Oracle Database 12c Backup and Recovery Survival Guide

Book Image

Oracle Database 12c Backup and Recovery Survival Guide

Overview of this book

The three main responsibilities of a successful DBA are to ensure the availability, recoverability, and performance of any database. To ensure the recoverability of any database, a DBA needs to have a strong backup and recovery skills set. Every DBA is always looking for a reference book that will help them to solve any possible backup and recovery situation that they can come across in their professional life. Oracle Database 12c Backup and Recovery Survival Guide has the unique advantage to be a reference to all Oracle backup and recovery options available, making it essential for any DBA in the world. If you are new to Oracle Database, this book will introduce you to the fantastic world of backup and recovery that is vital to your success. If you are an experienced DBA, this book will become a reference guide and will also help you to learn some possible new skills, or give you some new ideas you were never aware about. It will also help you to easily find the solution to some of the most well known problems you could find during your career as a DBA. This book contains useful screenshots, scripts, and examples that you will find more than useful. Most of the books currently available in the market concentrate only on the RMAN utility to backup and recovery. This book will be an exception to the rule and will become a must-have reference, allowing you to design a real and complete backup and recovery strategy. It covers the most important topics on Oracle database such as backup strategies, Nologging operations, new features in 12c, user managed backups and recoveries, RMAN (including reporting, catalog management, troubleshooting, and performance tuning), advanced data pump, Oracle Enterprise Manager 12c and SQL Developer. "Oracle Database 12c Backup and Recovery Survival Guide" contains everything a DBA needs to know to keep data safe and recoverable, using real-life scenarios.
Table of Contents (22 chapters)
Oracle Database 12c Backup and Recovery Survival Guide
Credits
About the Author
Acknowledgement
About the Author
Acknowledgement
About the Reviewers
www.PacktPub.com
Preface
Index

Redo-related wait events


There are a number of wait events that happen during redo activities and most of them are I/O related. First, I will talk about the two most important wait events: 'log file parallel write' and 'log file sync'. Then I will mention some other important ones you should know about.

The 'log file parallel write' event

Oracle foreground processes wait for 'log file sync', whereas the LGWR process waits for 'log file parallel write'. Although we usually find 'log file sync' in the Top 5 Timed Events or the Wait Events section of the Statspack report, in order to understand it we will first look at 'log file parallel write'.

The LGWR background process waits for this event while it is copying redo records from the memory log buffer cache to the current redo group's member log files on disk. Asynchronous I/O will be used if available to make the write parallel, otherwise these writes will be done sequentially one member after the other. However, LGWR has to wait until the I...