2Copyright © 2006, Oracle. All rights reserved.
Understanding the OracleData Guard Architecture
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Objectives
After completing this lesson, you should be able to do the following:
• Describe the Data Guard architecture
• Explain the operational requirements of Data Guard
• Describe how Data Guard processes, transports, and applies redo logs
• Describe standby database modes
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Data Guard Operational Requirements: Hardware and Operating System
• The hardware can be different for the primary and standby databases.
• The operating system and platform architecture for the primary and standby databases must be the same.
• The operating system releases for the primary and standby databases can be different.
• If all databases are on the same system, verify that the OS allows you to mount more than one database with the same name.
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Data Guard Operational Requirements: Oracle Database Software
• Same release of Oracle Database Enterprise Edition must be installed for all databases.
• SYSDBA privileges are required for the accounts used to manage the database instances.
• Each database must have its own control file.
• Primary database must operate in ARCHIVELOG mode.
• Enable FORCE LOGGING on the primary database before taking data file backups for standby creation.
• If any databases use ASM and/or OMF, all should use the same combination.
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Oracle Data Guard: Architecture
LGWR
Primary database
transactions
Onlineredologs
ARC0
FAL
RFS
MRP or LSP
Archived redo logs
ARC0
Standbydatabase
Reports
(MRP only)
Standbyredo logs
Archived redo logs
BackupOra
cle
net
LNSn
(Real-time apply)
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Primary Database Flow
LGWR
Primary database
transactions
Onlineredologs
ARC0
FAL
RFS
MRP or LSP
Archived redo logs
ARC0
Standbydatabase
Reports
(MRP only)
Standbyredo logs
Archived redo logs
BackupOra
cle
net
LNSn
(Real-time apply)
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Standby Database Flow
LGWR
Primary database
transactions
Onlineredologs
ARC0
FAL
RFS
MRP or LSP
Archived redo logs
ARC0
Standbydatabase
Ora
cle
net
Reports
(MRP only)
Standbyredo logs
Archived redo logs
Backup
LNSn
(Real-time apply)
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Standby Redo Logs
Redo from primary database
RFS ARC0
Standbyredo logs
Archivedredo logs
MRP/LSP
Standby database
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Physical Standby Database: Redo Apply Architecture
Physical standby database
Primary database
Productiondatabase
Physical standbydatabase
Redoapply
Redo stream
Redotransport
Backup
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Logical Standby Database:SQL Apply Architecture
Primarydatabase
Redo transport
Transform redo information into
SQL
SQL Apply
Reports
Productiondatabase
Logical standbydatabase
Logical standby database
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Redo records
LCRLCR
:
Shared pool
Transaction groups
Transactions sorted in
dependency order
Log Mining
Apply processing
Logical change records not grouped into transactions
Transactions to be applied
Reader Preparer Builder
AnalyzerCoordinatorApplier
Data files
Redo data from primary database
SQL Apply Process: Architecture
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Real-Time Apply
RFS
Standbyredo log
files
MRP or LSP
ARC0
Primary database
Standby database
Archivedredo log
files
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Setting the DB_UNIQUE_NAME Parameter
DB_UNIQUE_NAME = SF1_DB
San Francisco
SF1_DB
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Specifying Role-Based Destinations
Primarydatabase
Standbydatabase
LOG_ARCHIVE_DEST_2= location= "/u01/app/oracle/oradata/orcldg2/arc", valid_for=(STANDBY_LOGFILE,STANDBY_ROLE)DB_UNIQUE_NAME = HRDB2
Not used
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Combinations for VALID_FOR
Combination Primary Physical Logical
ONLINE_LOGFILE, PRIMARY_ROLE Valid Ignored Ignored
ONLINE_LOGFILE, STANDBY_ROLE Ignored Ignored Valid
ONLINE_LOGFILE, ALL_ROLES Valid Ignored Valid
STANDBY_LOGFILE,STANDBY_ROLE Ignored Valid Valid
STANDBY_LOGFILE, ALL_ROLES Ignored Valid Valid
ALL_LOGFILES, PRIMARY_ROLE Valid Ignored Ignored
ALL_LOGFILES, STANDBY_ROLE Ignored Valid Valid
ALL_LOGFILES, ALL_ROLES Valid Valid Valid
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Identifying Destination Settings
SQL> SELECT DEST_ID,VALID_TYPE,VALID_ROLE,VALID_NOW 2 FROM V$ARCHIVE_DEST;DEST_ID VALID_TYPE VALID_ROLE VALID_NOW------- --------------- ------------ -------------- 1 ALL_LOGFILES ALL_ROLES YES 2 STANDBY_LOGFILE STANDBY_ROLE WRONG VALID_TYPE 3 ONLINE_LOGFILE STANDBY_ROLE WRONG VALID_ROLE 4 ALL_LOGFILES ALL_ROLES UNKNOWN 5 ALL_LOGFILES ALL_ROLES UNKNOWN 6 ALL_LOGFILES ALL_ROLES UNKNOWN 7 ALL_LOGFILES ALL_ROLES UNKNOWN 8 ALL_LOGFILES ALL_ROLES UNKNOWN 9 ALL_LOGFILES ALL_ROLES UNKNOWN 10 ALL_LOGFILES ALL_ROLES UNKNOWN 11 ALL_LOGFILES ALL_ROLES YES11 rows selected.
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Standby Redo Log Configuration
Redo shipment
RFS
Standbyredo logs
Onlineredo logs
Primarydatabase
Standbydatabase
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Using SQL to Add Standby Redo Logs
• Use the ALTER DATABASE statement to create the standby redo log files:
• Add members to a group with the following statement:
• View information about the groups as follows:
SQL> ALTER DATABASE ADD STANDBY LOGFILE MEMBER 2 '/oracle/oradata/orcl/log2b.rdo' TO GROUP 2;
SQL> ALTER DATABASE ADD STANDBY LOGFILE 2 ('/oracle/oradata/orcl/log1c.rdo', 3 '/oracle/oradata/orcl/log2c.rdo') SIZE 500K;
SQL> SELECT * FROM v$standby_log;SQL> SELECT * FROM v$logfile 2 WHERE type = 'STANDBY';
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Using Enterprise Managerto Add Standby Redo Logs
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Standby Database Modes
You can maintain the standby data in one of the following modes:
• For physical standby databases– Redo Apply– Open read-only mode
• For logical standby databases– Open read/write mode
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Summary
In this lesson, you should have learned how to describe the following:
• Data Guard architecture processes
• Operational requirements of a Data Guard environment
• How Data Guard processes, transports, and applies redo logs
• Modes of standby databases and when to use each mode
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Practice 2-1: Architecture Review
This practice covers the following topics:
• Reviewing the Oracle Data Guard architecture
• Reviewing the processes that Data Guard uses to transport and apply redo logs
• Reviewing the modes that are used to recover a primary database
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Practice 2-2: Installing the Oracle Management Agent
This practice covers the following topics:
• Installing the Oracle Management Agent
• Configuring monitoring credentials for your database
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Practice 2-3: Configuring Your Primary Database
This practice covers the following topics:
• Reviewing your primary database configuration
• Configuring your primary database in preparation for creating a Data Guard configuration
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