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Lesson 3 View the Net Assistant
Objective Add a network node in Net Assistant.

View the Net Assistant

The Net Assistant was a GUI tool that helped DBA's configure Oracle communications. It supported wizards and configuration windows for the
  1. Net listener,
  2. Configuration Manager,
  3. Advanced Security, and
  4. Oracle database server nodes.
It reads and modifies the tnsname.ora file, the sqlnet.ora file, and the listener.ora file, which store configuration parameters for Oracle communications. The "tns" in tnsnames stands for Transparent Network Substrate, which is the technology built into Net that allows it to communicate with any standard network protocol (like TCP/IP). Even though manually created configuration files could be read and modified by the Oracle8i Net Assistant, many DBA's continued to manually support their configuration files as they have in the past.

Using Oracle Net Configuration Assistant to Configure Network Components

Oracle Net Configuration Assistant configures basic network components during installation, including:
  1. Listener names and protocol addresses
  2. Naming methods the client uses to resolve connect identifiers to connect descriptors
  3. Net service names in a tnsnames.ora file
  4. Directory server usage

Oracle Net Configuration Assistant runs automatically during software installation, as described in the Oracle Database installation guide. It can also be run after installation in standalone mode to configure naming methods, the listener, network service names in the tnsnames.ora file, and directory server usage. To start Oracle Net Configuration Assistant do the following:
  1. On Linux and UNIX, run netca from the ORACLE_HOME/bin directory.
  2. On Microsoft Windows, select Programs from the Start menu, and then select Oracle - HOME_NAME.
Next, select Configuration and Migration Tools, and then Oracle Net Configuration Assistant.

Net Assistant is deprecated and was replaced by Oracle Enterprise Manager (EM)

  1. This is the initial window of the Net Assistant. We will be creating a new database node. Begin by clicking the Net Service Names folder in the directory tree.
  2. Click the + button to start creating a new Net Service Name.
  3. The first page of the Net Service Name screen wizard appears. In this example, type TESTDB as the Net Service Name, then click Enter.
    Note: The name does not have to correspond with the SERVICE_NAME of the database. Press the Next button.
  4. Accept the default protocol of TCP/IP by clicking the Next button.
  5. Now, enter the name of the host computer on which the database service resides. For this example, type CAROLSPC and click the Next button. Accept the default port number of 1521.
  6. This page specifies the database instance into which this network node will connect. Since we are defining a node that contains an Oracle8i database, accept the radio button setting for Oracle8i release 8.1. For this example, type orcl.carol.org in the Service Name box and click the Next button. Accept the default port number of 1521.
  7. Here you can either continue or you can test the parameters you have specified. The test will try to connect to the database according to the parameters. Click the Test button to run a test.
  8. As you can see, the test begins immediately, using the standard user name of SCOTT and the password of TIGER. If the target database does not contain this user or the SCOTT user has a different password, you can specify a different username and password by clicking the Change Login button. Since our test worked, we will not do that. Click the Close button to continue.
  9. You are now ready to complete this node definition. Click the Finish button to end the wizard.
  10. The wizard has completed and the new database node is displayed in the Net Assistant window. Click the Advanced button in the right frame.
  11. This is where you can specify some of the new Net parameters, such as INSTANCE_NAME and MTS_DISPATCHERS (called Handler name in this window). The Use Dedicated Server check box sets the SRVR=DEDICATED parameter so that a dedicated service is used even if the database is set up as an MTS. The Use for Heterogeneous Services checkbox sets the HS = OK parameter and sets up this node for non-Oracle database connections. Click the Cancel button to exit this window.
  12. Now it is time to save the configuration to the tnsnames.ora file. Click the File menu selection.
  13. Click Save Network Configuration in the sub-menu selection.
  14. Once saved, you see the main Net Assistant screen again. Your new node has been saved in the tnsnames.ora file.

As you probably realized, all this wizard does is make an entry in our tnsnames.ora file. Here is how it will appear after this session; note the new ADDRESS_LIST parameter. 
# E:\ORACLE\ORA81\NETWORK\ADMIN\
   TNSNAMES.ORA 
   Configuration
File:E:\Oracle\Ora81\NETWORK\ADMIN\
   tnsnames.ora
# Generated by Oracle Net Assistant

TESTDB =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = 
      CAROLSPC
      (PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVICE_NAME = orcl.carol.org)
    )
  )

ORCL =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = 
      carolspc)
      (PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVICE_NAME = orcl.carol.org)
    )
  )

As you can see, the Net Assistant was a great tool for making easy changes to the parameter files. Because each database server and Oracle Net client has a tnsnames.ora file, most organizations create a "master" tnsnames.ora file and "push" the file to clients on a periodic basis. Tivoli Courier is commonly used for this task, but other software distribution tools work just as well. Remember, there are two cases in which you should add a multiple-service name for a single database:
  1. When you want to define multiple listeners (on separate posts) for a single database
  2. When you are using OPS and you want to add a Net service to map a request to another Oracle instance
The next lesson explores the entries in the parameter file (tnsnames.ora) maintained by the Net Assistant.

Add Net Service

Click the link below to practice adding another node yourself.
Add a Net service name by using the Net Assistant
You completed the steps and created the following entry into the tnsnames.ora file: 
PETS_ATLANTA =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = ATLANTA.EPETS.COM)
        (PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVICE_NAME = HOUSEOPETS)
    )
  )

Oracle Network Services

Oracle Network Services consists of three components:
  1. client:The client is the application or software that initiates the connection. It may be an end user application, such as a web page, or it may be another Oracle server.
  2. server: This is the software to which the client connects; it may be an Oracle server or an external procedure.
  3. listener: The listener (also known as the TNS listener or the Net Services listener) creates listen end points on the machine housing the Oracle server or external procedure. The addresses of these end points are established in advance and published in the tnsnames.ora file, stored in an Oracle Names server (the location of which is published in the names.ora file) or stored in some other name server.