Information the user passes to a service to connect, such as user name, password and connect identifier. For example:
CONNECT username/password@connect_identifier
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Load balancing, whereby the number of active connections among various instances and dispatchers for the same service are balanced. This enables listeners to make their routing decisions based on how many connections each dispatcher has and on how loaded the nodes that the instances run.
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A client connect request is forwarded to a another listener if the first listener is not responding. Connect-time failover is enabled by service registration, because the listener knows if an instance is running prior to attempting a connection.
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A database service can be accessed by more than one network route, or protocol address.
To add a network protocol address to an existing net service name or database service:
In the navigator pane, expand Oracle Net Configuration > Directory or Local > Service Naming.
Select a net service name or database service. The right pane displays the current destination service and address list.
In the Address Configuration box, choose plus (+). A new Address tab appears.
Select a protocol and enter the appropriate protocol parameter information for the selected protocol.
Order the addresses according to where it should be in the address list with the left-arrow and right-arrow buttons. Unless multiple address options are configured, only the first address in the list is contacted. To configure a different order, see Configure Multiple Address Options.
In the right pane, choose Apply.
If you are making these changes to the Local folder, choose File > Save Network Configuration.
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Oracle is a registered trademark of Oracle Corporation and/or its affiliates.
Other names may be trademarks of their respective owners.
An Oracle database is represented to clients as a service, that is, the database performs work on behalf of clients. A database can have one or more services associated with it.
Up to Oracle8i , an Oracle database service was uniquely identified by an Oracle System Identifier (SID). The SID was also used internally by the database as pointer to the System Global Area (SGA). Clients connected to a database instance by specifying the SID in the connect descriptor. This naming scheme did not distinguish services from instances.
Because an Oracle database can span over multiple computers, both the service as a whole and each of its instances are specified in Oracle9i and Oracle8i .
A database is now identified by its service name. The service name is specified by the SERVICE_NAMES parameter in the initialization parameter file. SERVICE_NAMES specifies the name of the highest-level view of Oracle database service, that may span instances and/or nodes. SERVICE_NAMES is defaulted to the global database name, a name comprised of the database name and domain name.
Database instances are identified by an instance name with the INSTANCE_NAME parameter in the initialization parameter file. INSTANCE_NAME corresponds to the SID of the instance.
Configure connect descriptors with the SERVICE_NAME (without an S) parameter to connect to an Oracle9i or Oracle8i database. For example, the following connect descriptor contains the address of a listener located on sales1-sun listening for connection requests for a database service called sales.us.example.com:
sales=
(DESCRIPTION=
(ADDRESS=(PROTOCOL=tcp)(HOST=sales-sun1)(PORT=1521))
(CONNECT_DATA=
(SERVICE_NAME=sales.us.example.com)))
Optionally, connect descriptors can be configured with the INSTANCE_NAME parameter to connect to a particular instance of the database. This may be necessary if you have an Oracle9 i Real Application Clusters with multiple instances.
For example, the following connect descriptor contains the address of a listener located on sales-sun1 listening for connection requests for an instance called sales1 associated with the sales.us.example.com database:
sales=
(DESCRIPTION=
(ADDRESS=(PROTOCOL=tcp)(HOST=sales-sun1)(PORT=1521))
(CONNECT_DATA=
(SERVICE_NAME=sales.us.example.com)
(INSTANCE_NAME=sales1)))
For more information about specifying an instance name in the CONNECT_DATA section of a connect descriptor, Chapter 13, Enabling Advanced Features for Oracle Net Services, in the Oracle10i Net Services Administrator's Guide.
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Oracle is a registered trademark of Oracle Corporation and/or its affiliates.
Other names may be trademarks of their respective owners.
A listener must exist on the server in order for the database to receive connections.
Note: During the installation process, a default listener named LISTENER is created.
To create a listener:
In the navigator pane, expand Oracle Net Configuration > Local > Listeners.
Choose plus (+) from the toolbar, or choose Edit > Create. The Choose Listener Name dialog box appears.
Accept the listener name provided in the Listener Name field, or edit the field with another name. By default the listener name is LISTENER for the first listener. Subsequent listener names are defaulted to LISTENERn . The listener name must be unique on any given node.
Choose OK.
Complete steps 4-6 in Configure Listener Addresses.
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Oracle is a registered trademark of Oracle Corporation and/or its affiliates.
Other names may be trademarks of their respective owners.
Note: Only users that are members of either the OracleNetAdmins or the OracleContextAdmins group can modify network information for a database service in a directory.
When database registration with the directory completes, Database Configuration Assistant creates a database service entry in the directory. By default, this entry contains network route information that includes the location of the listener through a protocol address. You can recreate this information, if it has been removed, or modify the existing network route information.
To create or modify network route information for a database service:
In the navigator pane, expand Oracle Net Configuration > Directory > Service Naming.
Select the database service. The right pane displays the current destination service name.
In the Address Configuration box, choose plus (+). A new Address tab appears.
Select a protocol and enter the appropriate protocol parameter information for the selected protocol.
In the right pane, choose Apply
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Other names may be trademarks of their respective owners.
A server that requires a dedicated server process for each user process. There is one server process for each client. Oracle Net sends the address of an existing server process back to the client. The client then re-sends its connect request to the server address provided. Contrast with shared server.
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Other names may be trademarks of their respective owners.
The Database Services tab enables you to specify the database services for which the listener must receive connect requests. The listener needs this information to connect a client to the database.
Oracle9i and Oracle8 i instances use dynamic service registration to inform the listener about their database services. Oracle7 and Oracle8 release 8.0 databases and Oracle Enterprise Manager tools require static service configuration in the listener.ora file.
Choose Add Database to add database service information.
Global Database Name
Enter the database name and domain name of the database as provided by the SERVICE_NAMES parameter value or DB_NAME and DB_DOMAIN parameter values in the initialization parameter file.
Oracle Home Directory
Enter the Oracle home location of the database.
Note: Windows NT already knows the Oracle home. Therefore, this field is not needed for a connection to a service on Windows NT.
SID
Enter the Oracle System Identifier (SID) for the instance.
Add Database button
Choose to configure service information for another database. A new Database tab displays where you can enter service information for another database.
Remove Database button
Choose to delete the selected Database tab and its service information.
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Oracle is a registered trademark of Oracle Corporation and/or its affiliates.
Other names may be trademarks of their respective owners.
A pointer that defines a one-way communication path from an Oracle database server to another database server. The link pointer is actually defined as an entry in a data dictionary table. To access the link, you must be connected to the local database that contains the data dictionary entry.
A database link connection is one-way in the sense that a client connected to local database A can use a link stored in database A to access information in remote database B, but users connected to database B cannot use the same link to access data in database A. If local users on database B want to access data on database A, then they must define a link that is stored in the data dictionary of database B.
The following database link types are supported:
A private database link in a specific schema of a database. Only the owner of a private database link can use it.
A public database link for a database. All users in the database can use it.
For mores information about creating private and public database links, see Oracle10i Database Administrator's Guide.
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Oracle is a registered trademark of Oracle Corporation and/or its affiliates.
Other names may be trademarks of their respective owners.