| Oracle&re
g; Data Guard Broker 10g Release 1 (10.1) Part Number B10822-01 |
|
|
View PDF |
| Oracle&re
g; Data Guard Broker 10g Release 1 (10.1) Part Number B10822-01 |
|
|
View PDF |
This chapter describes the Oracle Data Guard broker, its architecture and components, and how it automates the creation , control, and monitoring of a Data Guard configuration.
The following sections introduce Data Guard broker terminology and co ncepts:
< a href="#i1013106">Section 1.2, "Benefits of Data Guard Broker"
Section 1.7, "Oracle Data Guard Installation, Upgrade, Downgrade, and First Use"
See Oracle Data Guard Concepts and Administration for the definition of a Data Guard configu ration and for complete information about Oracle Data Guard concepts and terminology.
Oracle Data Guard ensures high availabi lity, data protection, and disaster recovery for enterprise data. Data Guard provides a comprehensive set of services that create, ma intain, manage, and monitor one or more standby databases to enable production Oracle databases to survive disasters and data corrupt ions. Data Guard maintains these standby databases as transactionally consistent copies of the primary database. If the primary datab ase becomes unavailable because of a planned or an unplanned outage, Data Guard can switch any standby database to the production rol e, thus minimizing the downtime associated with the outage. Data Guard can be used with traditional backup, recovery, and cluster tec hniques, as well as the Flashback Database feature to provide a high level of data protection and data availability.
A Data Guard configuration cons ists of one primary database and up to nine standby databases. The databases in a Data Guard configuration are connected by Oracle Ne t and may be dispersed geographically. There are no restrictions on where the databases are located if they can communicate with each other. For example, you can have a standby database on the same system as the primary database, along with two standby databases on another system.
The Data Guard broker logically groups these primary and standby databases into a broker configuration that allows the broker to manage and monitor them together as an integrated unit. You can manage them using the broker's graphical user interface (GUI) that is integrated with Oracle Enterprise Manager or using a command-line interface (CLI) called DGMGRL.
The Oracle Data Guard broker is a distributed management framework that automates and centralizes the creation, maintenance, and monitoring of Data Guard configurations. The following are some of the operations that the broker automates and simplifies:
Auto mated creation of Data Guard configurations incorporating a primary database, a new or existing (physical or logical) standby databas e, log transport services, and log apply services, where any of the databases could be Real Application Clusters (RAC) databases.
Adding up to 8 additional new or existing (physical or logical, RAC, or non-RAC) standby databases to each existing Data Guard configuration, for a total of one primary database, and from 1 to 9 standby databases in the same configuration.< /p>
Managing an entire Data Guard configuration, including all databases, log transport services, and log ap ply services, through a client connection to any database in the configuration.
Invoking switchover or f ailover with a single command to initiate and control complex role changes across all databases in the configuration.
Monitoring the status of the entire configuration, capturing diagnostic information, reporting statistics such as the l og apply rate and the redo generation rate, and detecting problems quickly with centralized monitoring, testing, and performance tool s.
You can perform all management operations locally or remotely through the broker's easy-to-use interfaces: the Data Guard web pages of Oracle Enterprise Manager, which is the broker's graphical user interface (GUI), and the Data Guard command-line interface (CLI) called DGMGRL.
These interfaces simplify the configurati on and management of a Data Guard configuration. Table 2-1 provides a comparison of configuratio n management using the broker's interfaces and using SQL*Plus.
The broker's interfaces improve usability and centralize ma
nagement and monitoring of the Data Guard configuration. Available as a feature of the Enterprise Edition and Personal Edition of the
Oracle database, the broker is also integrated with the Oracle database. These broker attributes result in the following benefits:
Disaster protection:
By automating the tasks required to configure and monitor a Data Guard configuration, the broker enhances the high availabi lity, data protection, and disaster protection capabilities that are inherent in Oracle Data Guard. Access is possible through a clie nt to any system in the Data Guard configuration, eliminating any single point of failure. If the primary database fails, the broker streamlines the process for any one of the standby databases to replace the primary database and take over production processing. The intersite availability that Data Guard provides makes it easier to protect your data.
While Oracle Data Guard broker enhances disa ster protection by maintaining transactionally consistent copies of the primary database, Data Guard, configured with Oracle high ava ilability solutions such as Real Application Clusters (RAC) databases, further enhances the availability and scalability of any given copy of that database. The intrasite high availability of a RAC database complements the intersite protection that is provided by Data Guard broker.
Consider that you have a cluster system hosting a primary RAC database comprised of multipl e instances sharing access to that database. Further consider that an unplanned failure has occurred. From a Data Guard broker perspe ctive, the primary database remains available as long as at least one instance of the clustered database continues to be available fo r transporting redo data to the standby databases. Oracle C luster Ready Services (CRS) manages the availability of instances of a RAC database. CRS works to rapidly recover failed instances to keep the primary database available. If CRS is unable to recover a failed instance, the Data Guard broker continues to run automatic ally with one less instance. If the last instance of the primary database fails, the Data Guard broker provides way to fail over to a specified standby database.
The Data Guard broker is integrated with CRS so that database role changes occur smoothly and sea mlessly. This is especially apparent in the case of a planned role switchover (for example, when a physical standby database is direc ted to take over the primary role while the former primary database assumes the role of standby). The Data Guard broker and CRS work together to temporarily suspend service availability on the primary database, accomplish the actual role change for both databases du ring which CRS works with the broker to properly restart the instances as necessary, then to resume service availability on the new p rimary database. The broker manages the underlying Data Guard configuration and its database roles while CRS manages service availabi lity that depends upon those roles. Applications that rely upon CRS for managing service availability will see only a temporary suspe nsion of service as the role change occurs within the Data Guard configuration.
Note that, while CRS enhances availability of a given copy of the RAC database, the Data Guard broker enhances availability of the data across multiple geographically dispersed lo cations, hence providing disaster protection. Together, broker and CRS provide a strong foundation for Oracle's high-availability arc hitecture.
The broker helps you to logicall y define and create a Data Guard configuration consisting of a primary database and a (physical or logical, RAC or non-RAC) standby database. The broker automatically communicates between the databases in a Data Guard configurati on using Oracle Net Se rvices. The database can be local or remote, connected by a LAN or geographically dispersed over a WAN.
The Data Guard GUI pro vides a wizard that automates the complex tasks involved in creating a broker configuration, including:
Adding an existing standby database, or a new standby database created from existing backups taken through the Data Guard GUI
Configuring the standby control file, server parameter file, and datafiles
Initial izing communication with the standby databases
Creating online redo log files
Although the CLI cannot automatically create a new standby database, the CLI can configure and monitor an existing standby database, including those created by the Data Guard GUI.
After you create a Data Guard configuration consisting of a primary and standby database, you can add up to eight new or existing, physical or logical standby databases to each Data Guard configuration. The Data Guard GUI p rovides an Add Standby Database wizard to guide you through the process of adding more databases. The GUI also makes all Oracle Net S ervices configuration changes necessary to support log transport services and log apply services across the configuration.
You can issue commands to:
Simplify the management of all components of the configuration, including the primary and standby database s, log transport services, and log apply services.
Coordinate database state transitions and update data base properties dynamically with the broker recording the changes in a broker configuration file that includes profiles of all the da tabases in the configuration. The broker propagates the changes to all databases in the configuration and their server parameter file s.
Simplify the control of the configuration protection modes (to < a id="sthref45" name="sthref45">maximize protection, to maximize availability, or to maximize performance).
Invoke the GUI's < /a>verify operation to ensure that log transport services and < /a>log apply services are configured and functioning properly.
Only one command is required to initiate complex role changes for switchover or failover operations across all databases
in the configuration. The broker automates switchover and failover to a specified standby database in the broker configuration. The
GUI enables you to select a new primary database from a set of viable standby databases (enabled and online, with normal status). The
CLI SWITCHOVER and FAILOVER commands only require you to specify the target standby database before automa
tically initiating and completing the many steps in switchover or failover operations across the multiple databases in the configurat
ion.
The broker provides built-in validation that monitors the health of all of the databases in the configuration. F rom any system in the configuration connected to any database, you can capture diagnostic information and detect obvious and subtle p roblems quickly with centralized monitoring, testing, and performance tools. Both the GUI and the CLI retrieve a complete configurati on view of the progress of log transport services on the primary database and the progress of log apply services on the standby datab ase. The GUI and the CLI also retrieve data specific to physical and logical standby databases.
The ability to monitor local and remote databases and respond to events is significantly enhanced by the broker's health check mechanism and the GUI 's tight integration with the Oracle Enterprise Manager eve nt management system.
Use of the broker is possible for any database because the broker works transparently with ap plications; no application code changes are required to accommodate a configuration that you manage with the broker.
|
See Also: Oracle Data Guard Concepts and Administration for a complete description of the discrete steps that comprise the creation of standby databases and the other monitoring and control operations that have been automat ed or simplified by the broker. |
The broker simplifies the management of a Data Guard environment by performing operations upon the following logical objects:
The broker supports one or more Data Guard conf igurations, each of which includes a profile for one primary database and for up to nine physical or logical, RAC or non-RAC standby databases. A supported broker configuration consists of:
A
configuration object, which is a named collection of database profiles. A database
Database objects, corresponding to primary or standby databases. The broker uses a database object's profile to manage and control the state of a single database on a given system. The database object may be comprised of one or more instance objects if this is a RAC database.
Instance objects. The bro ker treats a database as a collection of one or more named instances. The broker automatically discovers the instances and associates them with their database.
Figure 1-1 shows the relationship of these objects.
Figure 1-1 Relationship of Objects Managed by the Data Guard Broker
You can perform complex operations on a sing le database or on all databases in an entire configuration with a single mouse click or CLI command. You can enable or disable broker management of each database in a configuration one at a time. Or, if desired, enable or disable them all at the same time in a singl e step by enabling or disabling the configuration itself.
|
See also: Chapter 2, Ch apter 3, and Chapter 4 for more information about managing configuration and database obj ects |
The Oracle Data Guard broker consists of the following components:
The Data Guard graphical user interface, tightly integrated with Oracle Enterpri se Manager, and the Data Guard command-line interface are the broker client interfaces that help you define and manage a configuratio n consisting of a collection of primary and standby databases. Section 1.5 describes these interfaces in more detail.
The Data Guard monitor is the broker server-side component that is integrated with the Oracle database. Data Guard mo nitor is composed of the DMON process and broker configuration files that allow you to control the databases of that configuration, m odify their behavior at runtime, monitor the overall health of the configuration, and provide notification of other operational chara cteristics. Section 1.6 describes the Data Guard monitor in more detail.
Figure 1- 2 shows these components of the broker.
You can use either of the broker's user interfaces to create a broker confi guration and to control and monitor the configuration. The following sections describe the broker's user interfaces:
The Data Guard GUI is a graphical user interface that works with the Data Guard monitor and Oracle Enterprise Manager to automate and simplify the management of a Data Guard configuration. Because it is integrated with Oracle Enterprise Manager, the Data Guard GUI enables you to manage your configuration using a familiar i nterface and event management system.
With the Data Guard GUI, the complex operations of creating and managing standby databases are simplified thro ugh wizards provided by the Data Guard GUI. The Data Guar d GUI includes:
An Add Standby Database wizard that helps you to create a broker configuration, if one does not already exist, having a primary database and a local or remote standby database. The wizard can create a physical or logical standby database (non-RAC) or import an existing physical or logical (RAC or non-RAC) standby database. If the wizard creates a physical or logical standby database, the wizard also automates the creation of the standby control file, server pa rameter file, online redo log files, and the standby datafiles.
A switchover operation that helps you switch roles between the primary database and a standby database.
A failover operation that changes one of the standby dat abases to the role of a primary database.
Performance tools and graphs that help you monitor and tune log transport services and log apply services.
< /a>Property pages that allow you to set database properties on any database and, if applicable, the settings are immediately propagat ed to all other databases and server parameter files in the configuration.
Integration with Oracle Enter prise Manager to perform event reporting through e-mail .
In addition, it makes all Oracle Net Services configuration changes necessary to support lo g transport services and log apply services.
Figure 1-3 shows t he overview page from the Data Guard GUI in Oracle Enterprise Manager.
Figure 1-3 Data Guard GUI (in Oracle Enterprise Manager) - Overview Page
|
See Also: The Data Guard GUI online hel p |
T he Data Guard command-line interface (CLI) enables you to control and monitor a Data Guard configuration from the CLI prompt or within scripts. You can perform most of the activities requi red to manage and monitor the databases in the configuration using the CLI.
The followi ng example lists the available commands:
DGMGRL> HELP
The fo
llowing commands are available:
add Add a standby database into the broker configuration
connect Connect to an Ora
cle instance
create Create a broker configuration
disable Disable broker control of a configuration or database
edit
Edit a configuration, database or instance
enable Enable broker control of a configuration or database
exit
Exit the program
failover Change a standby database to be the primary database
help Display description and syntax
for a given command
quit Exit the program
rem Comment to be ignored by DGMGRL
remove Remove a configurat
ion, database or instance
show Display information of a configuration, database or instance
shutdown Shut down a curr
ently running Oracle instance
startup Start an Oracle database instance
switchover Switch roles between the primary databa
se and a standby database
Use "help <command>" to see syntax for individual commands.
The configuration, control, and monitoring functions of the broker are implemented by server-side software and configuration files that are maintaine d for each database that the broker manages. The software is called the Data Guard monitor.
The following sections describe ho w the Data Guard monitor interacts with the Oracle database and with remote Data Guard monitors to manage the broker configuration.
The Data Guard monitor process (DMON) is an Oracle background process that runs for every database instance that is managed by the broker. When you start the Data Guard broker, a DMON process is created.
When you use the Data Guard GUI o r the CLI to manage a database, the DMON process is the server-side component that interacts with the local database and the DMON pro cesses of the other databases to perform the requested function. The DMON process is also responsible for monitoring the health of the broker configu ration and for ensuring that every database has a consistent description of the configuration.
|
See Also: Oracle Database Concepts for more information about the memory structures and processes that are used with an Oracle database |
Figure 1-4 shows the broker's DMON process as one of several background proc esses that constitute an instance of the Oracle database. Figure 1-4 shows multiple databases, each having it s own DMON process. This distributes the broker across all of the databases of the broker configuration.
Fi gure 1-4 Databases With Distributed Broker (DMON) Processes
The zigzag arrow in the center of Figure 1-4 represents the two-way Oracle Net Servi ces communication channel that exists between the DMON processes of two databases in the same broker configuration.
This two-way communication channel is used to pass requests between databases and to monitor the health of all of the da tabases in the broker configuration.
When creating a new Data Guard configuration or adding a new standby database into an exi sting configuration, the DMON process uses an initial connect identifier to connect to the database to collect necessary information about the database. This initial connect identifier is supplied by the user if the CLI is used, or constructed automatically if the G UI is used.
After the initial connection, the DMON process constructs connect descriptors for communication with other DMON pr
ocesses on other databases, using the address value from the LOCAL_LISTENER initialization parameter from those database
s. The DMON processes automatically manage the connections to each other. If a database is a RAC database, then as long as one instan
ce in the database is running and the DMON process is started on the instance, that DMON process is able to establish two-way communi
cations with other DMON processes on other databases to manage the database as part of the Data Guard configuration.
The broker's DMON process persis tently maintains profiles about all database objects in the broker configuration in a binary configuration file. A copy of this file is maintained by the DMON process for each of the databases that belong to the broker configuration. Each database's copy of the fil e is shared by all instances of the database if it is a RAC database. Changes to this file are made by the DMON process for all copie s.
This configuration file contains profiles that describe the states and properties of the databases in the configuration. Fo r example, the file records the databases that are part of the configuration, the roles and properties of each of the databases, and the state of each database in the configuration.
The configuration data is managed transparently by the DMON process to ensure that the configuration information is kept consistent across all of the databases. The broker uses the data in the configuration file to configure and start the databases, control each database's behavior, and provide informat ion to the CLI and the Data Guard GUI. (See Section 3.3 for more information.)
Whenever you add databases to a broker configuration, or make a change to an existing database's properties, each DMON process records the new information in its copy of the configuration file.
Associated with each database are various properties t hat the DMON process uses to control the database's behavior. The properties are recorded in the configuration file as a part of the database's object profile that is stored there. Many database properties are used to control database initialization parameters relat ed to the Data Guard environment.
To ensure that the broker can update the values of parameters in both the database itself an d in the configuration file, you must use a server para meter file to control static and dynamic initialization parameters. The use of a server parameter file gives the broker a mechanism t hat allows it to reconcile property values selected by the database administrator (DBA) when using the broker with any related initia lization parameter values recorded in the server parameter file.
When you set values for database properties in the broker con figuration, the broker records the change in the configuration file and propagates the change to all of the databases in the Data Gua rd configuration.
Oracle Data Guard, the Data Guard monitor, and the Data Guard command-line in terface (DGMGRL) are included with the Enterprise Editi on or Personal Edition of the Oracle database software.
The Data Guard graphical user i nterface (GUI) is included with the Oracle Enterprise Manager software.
Note:
In Oracle9i, the Data Guard GUI was called Data Guard Manager and was u sable either through the Oracle Enterprise Manager Console or by invoking it directly from the command line. In Oracle Database 10g, it is tightly integrated with Oracle Enterprise Manager and is referred to as the Data Guard GUI.The Oracle Data Guard graphical user interface (GUI), which you can use t o manage broker configurations, is installed with the Oracle Enterprise Manager software.
< /div>If you are currently running an Oracle Data Guard release 9.0.n configuration, you must upgrade to Oracle Database release 10.1 and re-create the broker configuration, as follows:
Delete (remove) the release 9.0.n broker configuration using the same release of either Data Guard Mana
ger or the CLI. For example, the CLI REMOVE CONFIGURATION command can be used.
Upgrade the database sof tware to Oracle Database release 10.1. See the Oracle installation documentation that is appropriate for your operating system.
If you are using Oracle Enterprise Manager and Data Guard Manager release 9.0.n, you must upgrade to Oracle Enterprise Manager release 10.1 to manage a broker configur ation running Oracle Data Guard release 10.1:
Data Guard Manager release 9.0.n is not compatibl e with Oracle Data Guard release 10.1.
Data Guard GUI release 10.1 is not compatible with Oracle Data Gu ard release 9.0.n. You will receive an error message stating that the Oracle database is too old.
If you are using the CLI release 9.0.n, you must upgrade to Data Guard command-line interface release 10.1:
The CLI release 9.0.n is not compatible with Oracle Data Guard release 10.1.
|
Note: Existing Oracle9i command-line scripts are supported in Oracle D atabase 10g for non-RAC databases. See Appendix A for information about deprecated commands. |
The CLI release 10.1 is not co mpatible with Oracle Data Guard release 9.0.n.
|
Note: Oracle Database 10g command-line scripts are not supported in Oracle9i. |
Invoke the Data Guard GUI or the CLI, and re-create the broker configu ration.
|
See Also: See Oracle Database Upgrade Guide if you are upgrading from Oracle8i Data Guard to Oracle Data Guard |
If yo u are currently running an Oracle Data Guard release 9.2.0 configuration, you must upgrade to Oracle release 10.1, and re-create the broker configuration, as follows:
Delete (remove) the rele
ase 9.2.0 broker configuration using Data Guard Manager or the CLI release 9.2.0. For example, the CLI REMOVE CONFIGURATION command can be used.
If using the CLI, clear the LOG_ARCHIVE_DEST_n initializ
ation parameter settings by using the ALTER SYSTEM SET LOG_ARCHIVE_DEST_n=" " SQL*Plu
s command.
Upgrade the database software to Oracle release 10.1. See the Oracle Database installation documentation that is appropriate for your operating system.
If you are using Oracle Enterprise Manager and Data Guard Manager release 9.2.0, you must upgrade to Oracle Enterprise Manag er release 10.1 to manage a broker configuration running Oracle Data Guard release 10.1. Data Guard Manager release 9.2.0 is not comp atible with Oracle Data Guard release 10.1.
If you are using the CLI release 9.2.0, you must upgrade to Data Guard c ommand-line interface release 10.1:
The CLI release 9.2.0 is not compatible with Oracle Data Guard relea se 10.1.
|
Note: Existing Oracle9i comm and-line scripts are supported in Oracle Database 10g for non-RAC databases. See Appen dix A for information about deprecated commands. |
The CLI release 10.1 is not compatible with Oracle Data Guard release 9.2.0.
|
Note: Oracle Database 10g command-line scripts are not supported in Oracle9i< /em>. |
Invoke the Data Guard GUI or the CLI, and re-create the broker configuration.
If you have upgraded to release 10.1 and want to downgra de to your prior release, you must downgrade the database release and re-create the broker configuration as follows:
Delete (remove) the release 10.1 broker configuration using the Data Guard GUI or the CLI release 10.1. For examp
le, the CLI REMOVE CONFIGURATION command can be used.
Downgrade the database software to your prior Ora cle release. See the Oracle database documentation that is appropriate for your operating system.
If you are downgra ding to Oracle release 9.2.0 and you were using the Data Guard GUI, you may continue to use the Data Guard GUI in Oracle Enterprise M anager release 10.1 to manage your 9.2.0 broker configuration. You may also downgrade to the Data Guard Manager by re-installing Orac le Enterprise Manager release 9.2.0.
If you are downgrading to Oracle release 9.0.n and you were using the Data Guard GUI, you must downgrade to the Data Guard Manager by re-installing Oracle Enterprise Manager release 9.0.n. The O racle Database 10g Data Guard GUI is not compatible with Oracle Data Guard release 9.0.n.
Invoke t he Data Guard Manager or the CLI and re-create the broker configuration.
The foll owing conditions must be true before you can use the br oker:
The primary and standby databases must be running Oracle 10 .1 and each can be installed in either a single-instance or multi-instance environment. The database must be licensed for Oracle Ente rprise Edition or Personal Edition.
You must use a server parameter file (SPFILE) to ensure the broker can persistently reconcile values between broker properties and any related initialization parameter values. See Sec tion 3.3.2 for more information.
The value of the DG_BROKER_START parameter must be set to TRUE. See Section 2.3 for more information. (Data Guard GUI sets this parameter automatically.)
If any of the databases in the configuration is a RAC database, you must set up the DG_BROKER_CON
FIG_FILEn initialization parameters for that database such that they point to the same shared files for
all instances of that database. The default values for these parameters will not work. The shared files could be files on a cluster f
ile system, if available, or on raw devices.
|
See Also: See Section 1.6.2 for information about the configuration file. See Section 2.2 for details about setting up the broker configuration file. See Section 2.2.1 for details about sizing the raw devices. |
Oracle Net Services network files must be set up on the primary database and on the standby database if you configure an existing standby d atabase into the broker configuration. Otherwise, the Data Guard GUI automatically sets up the network files when it creates a standb y database.
The LOCA
L_LISTENER initialization parameter on each instance that is part of a Data Guard broker configuration must resolve to a liste
ner address that is reachable by all members of the configuration. See the Oracle Database Reference and the Oracle Ne
t Services Administrator's Guide for additional information.
To enable the Data Guard broker's
CLI to restart instances during the course of broker operations, a service with a specific name must be statically registered with th
e local listener of each instance. The value for the GLOBAL_DBNAME attribute must be set to a concatenation of db_unique_name_DGMGRL.db_domain. For example, in the listener.ora file:
LISTENER = (DESCRIPTION =
(ADDRESS_LIST=(ADDRESS=(PROTOCOL=tcp)(HOST=host_name)
(PORT=port_n
um))))
SID_LIST_LISTENER=(SID_LIST=(SID_DESC=(SID_NAME=sid_name)
(GLOBAL_DBNAME=db_unique_name_DGMGRL.db_domain)
(ORACLE_HOME=oracle_home)))
Any database, including instances of the database, managed by the broker must be mounted.
If any of the databases in the configuration is a RAC
database, the START_OPTIONS for that database must be set to MOUNT in the Oracle Cluster Repository (OCR) u
sing SRVCTL as follows:
SRVCTL ADD DATABASE -d <db_unique_name> -o <$ORACLE_HOME> -s MOUNT or SRVCTL MODIFY DATABASE -d <db_unique_name> -o <$ORACLE_HOME> -s MOUNT
You must set the COMPATIBLE initialization parameter to 9.2.0 or higher for both the primary and standby da
tabases.
|
See Also: Section 2.3 for more information about preparing and starting the Oracle Data Guard broker. See Oracle Data Guard Concepts and Administration for more information about set ting up the network files. |
|
 Copyright © 2000, 2003 Oracle Corporation All Rights Reserved. |
|
