Book Image

Oracle Data Guard 11gR2 Administration : Beginner's Guide

Book Image

Oracle Data Guard 11gR2 Administration : Beginner's Guide

Overview of this book

Data Guard is the high availability, disaster recovery and data replication solution for Oracle Databases. With the huge growth of Data Guard it's getting harder to encounter an Oracle DBA not dealing with Data Guard. Since it's a common DBA task to provide high availability of databases, Data Guard is a must-know topic for every Oracle Database Administrator."Oracle Data Guard 11g R2 Beginner's Administration Guide" is a practical guide that provides all the information you will need to configure and maintain Data Guard. This book will show you what Data Guard can really do.By following the practical examples in this book, you'll learn to set up your Data Guard Broker, the management framework for Data Guard configurations. Learn and implement different data protection modes, perform role transitions between databases (switchover and failover) and configure Active Data Guard. Next, we will dive into the features of Snapshot Standby. The book progresses into looking at Data Guard configuration with other Oracle products (such as EM, RAC, and RMAN) and patch databases in Data Guard. The final chapters will cover commonly encountered Data Guard issues and Data Guard best practices, which are very important to make a Data Guard configuration perfect and take maximum advantage of Data Guard properties.
Table of Contents (19 chapters)
Oracle Data Guard 11gR2 Administration Beginner's Guide
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Pop Quiz Answers
Index

Time for action – verifying synchronization between the primary and standby databases


By using the following steps, you can control whether the standby database is synchronized with primary:

  1. On the standby database, query the V$ARCHIVED_LOG view for the archived and applied sequences.

    For the last archived sequence, use the following:

    SQL> SELECT MAX(SEQUENCE#) FROM V$ARCHIVED_LOG;
    MAX(SEQUENCE#)
    --------------
               145
    

    For the last applied sequence, use the following:

    SQL> SELECT MAX(SEQUENCE#) FROM V$ARCHIVED_LOG WHERE APPLIED='YES';
    MAX(SEQUENCE#)
    --------------
               144
    

    From the preceding two queries, we see that the latest sequence, 145, is being archived or written into the standby redo logfiles. There's expected to be a lag of one sequence between archived and applied columns.

  2. Check the status of the latest log sequence.

    SQL> SELECT SEQUENCE#,APPLIED FROM V$ARCHIVED_LOG ORDER BY SEQUENCE#;
    
     SEQUENCE# APPLIED
    ---------- ---------
           140 YES
           141 YES
      ...