Interaction Between the Data Guard Broker and a Data Guard Configuration [ID 249703.1]
| Interaction Between the Data Guard Broker and a Data Guard Configuration [ID 249703.1] |
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Modified 20-OCT-2010Type FAQStatus PUBLISHED |
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PURPOSE
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This bulletin will show details about DataGuard, what it is and how it makes it
easier to manage your Standby databases. It also shows the interaction between
the DataGuard configuration and the database.
SCOPE & APPLICATION
-------------------
Intented to be used for administrators managing or planning to implement a
Data Guard (Broker) environment.
1. Data Guard Broker and Standby Database
-----------------------------------------
Basically, it is possible to create/run a Physical/Logical standby database
without the Data Guard Broker (see notes in "Related Documents"). The Data Guard
Broker itself is an offset to the Standby database making maintainance and
administration of several Standby databases much easier. Data Guard Broker uses
an own process (DMON) on each Primary/Standby database and own configuration
files for interaction.
The process is started if you set the initialization parameter
'DG_BROKER_START' to TRUE. To create and maintain the configuration files, you
need to create a Data Guard configuration either using the Data Guard wizard
from Enterprise Manager Grid Control, resp. the DataGuard Manager or you do this
manually using the command line DGMGRL. Both procedures are also shown in Notes
refered in "Related Documents".
2. The DataGuard Configuration
------------------------------
Once you created a Data Guard Broker configuration using one of the ways
mentioned above, you have a basic Data Guard Broker configuration running.
This configuration has its own parameters and settings. They are maintained in
the DataGuard metadata configuration files. There exist two configuration files
on each Site. These files must also be accessible from the database, therefore,
the initialization parameter 'DG_BROKER_CONFIG_FILEn' points to the corresponding
configuration files. These files and all related settings are only altered or
maintained if the configuration is created and enabled. DO NOT edit these
files manually. They are binary files, editing them with an editor can destroy
these files and your DataGuard configuration !!
If the database (Primary and/or Standby database) is a RAC database (10.1.0+),
then all instances have to use the same Data Guard Broker configuration files,
ie. they have to reside on the shared disk (RAW devices, CFS or ASM).
3. The Control of DataGuard
---------------------------
The Data Guard Broker configuration can either be administered via the Data
Guard Manager GUI as part of the Enterprise Manager (Grid Control) or via the
Data Guard Manager command line DGMGRL. All are cooperating with each other and
make sure the Data Guard Broker configuration information is consistant. So
they all revert to the same configuration files as mentioned before. So all
changes you make on the Data Guard Manager impacting the configuration files
and the database resp. its parameters. The advantage you have here is that you
do not have take care of the database parameters and status, Data Guard Broker
does this for you and you can administer the Primary and Standby database either
using the GUI or some simple commands in the command line interface. The changes/
commands you run on the DataGuard Manager are executed on either the Primary or
Standby or both, depending on the command. There's no separate connection from
you to the databases required and Data Guard Broker decides which databases are
related to your command.
4. Interaction between Data Guard Broker and the Primary/Standby Database
--------------------------------------------------------------------------
By setting the initialization parameter 'DG_BROKER_START' to TRUE, the
Data Guard Broker Managing Process (DMON) is started. This process must be
started on all databases (Primary and Standby) involved in the configuration.
The DMON process reads the configuration files on its site and sets the
required database parameter accordingly, eg. in the Data Guard Manager you set
the parameter 'STANDBY_ARCHIVE_DEST' to a certain value. This value will be
written into the corresponding DataGuard configuration file. The DMON sees this
information and updates the database parameters accordingly. A prerequisite for
this functionality to run correctly is the usage of a Server-parameterfile
(SPFILE), of course.
5. Troubleshooting
------------------
Most problems come from a wrong Data Guard configuration or misplaced settings
in the Data Guard configuration files. If any problem occurs you first
of all should sort out if this is a Data Guard Broker or Standby database
problem. So you can either try to disable your configuration or set
'DG_BROKER_START' to FALSE and verify your Standby database still works
correctly. If this is not the case, it seems to be a Standby database issue, so
see the ALERT.LOG-files from Primary and Standby database for more Hints. If
your Standby database still works well it is most likely you have a problem
with Data Guard Broker. Many hints mostly can be found in the DRC<SID>.LOG-file,
which is written by the DMON. This file can be found in the same directory
where the ALERT.LOG is located on each instance part of the configuration.
Wrong settings and communication problems are mostly logged there.
RELATED DOCUMENTS
-----------------
Data Guard, Concepts and Administration
Data Guard Broker
Note:180031.1: Creating a Data Guard configuration
Note:186150.1: Data Guard 9i Creating a Logical Standby database
Note:214071.1: Creating a configuration using Data Guard Manager
Note:201669.1: Setup and maintenance of Data Guard Broker using DGMGRL
Note:745201.1: Diagnosing Connection Problems with an active Data Guard Broker configuration
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