In a distributed database system, each database should have a unique global database name. Global database names uniquely identify a database in the system. A primary administration task in a distributed system is managing the creation and alteration of global database names. This section contains the following topics:
Understanding How Global Database Names Are Formed
A global database name is formed from two components: a database name and a domain. The database name and the domain name are determined by the following initialization parameters at database creation:
Component Parameter Requirements Example
These are examples of valid global database names:
The DB _DOMAIN initialization parameter is only important at database creation time when it is used, together with the DB _NAME parameter, to form the database global name. At this point, the database global name is stored in the data dictionary. You must change the global name using an ALTER DATABASE statement, not by altering the DB _DOMAIN parameter in the initialization parameter file. It is good practice, however, to change the DB _DOMAIN parameter to reflect the change in the domain name before the next database startup.
Determining Whether Global Naming Is Enforced
The name that you give to a link on the local database depends on whether the remote database that you want to access enforces global naming. If the remote database enforces global naming, then you must use the remote database global database name as the name of the link. For example, if you are connected to the local hq server and want to create a link to the remote mfg database, and mfg enforces global naming, then you must use the mfg global database name as the ink name.
You can also use service names as part of the database link name. For example, if you use the service names sn1 and sn2 to connect to database hq.acme.com, and hq enforces global naming, then you can create the following link names to hq:
To determine whether global naming on a database is enforced on a database, either examine the database initialization parameter file or query the V$PARAMETER view. For example, to see whether global naming is enforced on mfg, you could start a session on mfg and then create and execute the following globalnames.sql script (sample output included):
Viewing a Global Database Name
Use the data dictionary view GLOBAL_NAME to view the database global name. For example, issue the following:
Changing the Domain in a Global Database Name
Use the ALTER DATABASE statement to change the domain in a database global name. Note that after the database is created, changing the initialization parameter DB _DOMAIN has no effect on the global database name or on the resolution of database link names.
The following example shows the syntax for the renaming statement, where database is a database name and domain is the network domain:ALTER DATABASE RENAME GLOBAL_NAME TO database.domain;
Use the following procedure to change the domain in a global database name:
Changing a Global Database Name: Scenario
In this scenario, you change the domain part of the global database name of the local database. You also create database links using partially specified global names to test how Oracle Database resolves the names. You discover that the database resolves the partial names using the domain part of the current global database name of the local database, not the value for the initialization parameter DB _ DOMAIN.
The database expands the global database name for this link by appending the domain part of the global database name of the local database to the name of the database specified in the link.
This result indicates that the domain part of the global database name of the local database is us.acme.com. The database uses this domain in resolving partial database link names when the database link is created.
This result indicates that the value of the DB _DOMAIN initialization parameter is independent of the ALTER DATABASE RENAME GLOBAL _NAME statement. The ALTER DATABASE statement determines the domain of the global database name, not the DB _DOMAIN initialization parameter (although it is good practice to alter DB _DOMAIN to reflect the new domain name).
This result indicates that the database resolves the partially specified link name by using the domain jp.acme.com. This domain is used when the link is created because it is the domain part of the global database name of the local database. The database does not use the DB_DOMAIN initialization parameter setting when resolving the partial link name.
The result indicates that the domain setting in the parameter file is exactly the same as it was before you issued either of the ALTER DATABASE RENAME statements.
Again, you see that the database uses the domain part of the global database name of the local database to expand the partial link name during link creation.
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Oracle 10g Tutorial
Overview Of Administering An Oracle Database
Creating An Oracle Database
Starting Up And Shutting Down
Managing Oracle Database Processes
Managing Control Files
Managing The Redo Log
Managing Archived Redo Logs
Managing Datafiles And Tempfiles
Managing The Undo Tablespace
Using Oracle-managed Files
Using Automatic Storage Management
Managing Space For Schema Objects
Managing Partitioned Tables And Indexes
Managing Hash Clusters
Managing Views, Sequences, And Synonyms
General Management Of Schema Objects
Detecting And Repairing Data Block Corruption
Managing Users And Securing The Database
Managing Automatic System Tasks Using The Maintenance Window
Using The Database Resource Manager
Moving From Dbms_job To Dbms_scheduler
Overview Of Scheduler Concepts
Using The Scheduler
Administering The Scheduler
Distributed Database Concepts
Managing A Distributed Database
Developing Applications For A Distributed Database System
Distributed Transactions Concepts
Managing Distributed Transactions
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