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Installing Oracle9iAS Discoverer on multiple machines

Discoverer Plus and DiscovererViewer are automatically installed to run with Oracle9i Application Server as a single machine installation. However Oracle9iAS Discoverer is designed to be deployed on multiple machines. The Discoverer Services can be replicated by specifying the machines available to Discoverer in a configuration file. Discoverer Services sessions are then started on alternate machines to balance the load.

In this way very large numbers of Discoverer users can be supported, since there is no single bottleneck. Multiple Discoverer sessions can run on a single machine, or can be spread across multiple machines as required.

The topics include:

• What are the differences between a default installation and a distributed installation of Oracle9iAS Discoverer?

• Performing a distributed installation

3.1 What are the differences between a default installation and a distributed installation of Oracle9iAS Discoverer?

3.1.1 Default installation of Oracle9iAS Discoverer

Oracle9iAS Discoverer is installed as part of Oracle9i Application Server. The default installation is a single machine installation (i.e. all the Discoverer components are installed on a single machine).

Figure 3-1 Oracle9iAS Discoverer Default Configuration on a single machine

In this scenario, the Oracle 9i Application Server installation has installed both of the following on the same machine:

• HTTP Server software

• all the Discoverer Services components (Locator, Session, Preferences, SmartAgent, and Object Activation Daemon)

The machine is therefore both an HTTP Server machine and an Application Server machine.

When a user launches a web browser on a client machine to start Oracle9iAS Discoverer, the web browser sends a request to the HTTP Server software on the server machine. That request is processed and a Discoverer session is started on the server machine.

3.1.2 Distributed Oracle9iAS Discoverer installation

Having a single machine acting as both the HTTP Server machine and the Application Server machine can be inefficient when supporting large numbers of Discoverer users.

For this reason, the Discoverer Services components are designed to be deployed on multiple machines. By specifying the available machines in a configuration file, Discoverer Services sessions can be started on different machines to balance the load. Multiple Discoverer sessions can run on a single machine, or can be spread across multiple machines as required.

Figure 3-2 Oracle9iAS Discoverer multiple machine configuration

In this scenario (as with a default installation), the Oracle 9i Application Server installation has installed both of the following on the same machine:

• HTTP Server software

• all the Discoverer Services components (Locator, Session, Preferences, SmartAgent, and Object Activation Daemon)

The machine is therefore both an HTTP Server machine and an Application Server machine. This machine is referred to as the Master Discoverer Server machine.

In addition to the Master Discoverer Server, you can also install the Oracle 9i Application Server on additional machines. These machines are referred to as Additional Discoverer Server machines.

When a user launches a web browser on a client machine to start Oracle9iAS Discoverer, the web browser sends a request to the HTTP Server software on the Master Discoverer Server machine. That request is processed and a Discoverer session is started either on the Master Discoverer Server machine or on an Additional Discoverer Server machine.

Each Additional Discoverer Server machine can run multiple sessions; therefore, the number of machines you choose to use for sessions depends on how many concurrent sessions the users need, the amount of memory available, the speed of the hardware, and so on.

3.2 Performing a distributed installation

3.2.1 Confirming connection to the default Master Discoverer Server machine

Before you start altering the default installation, we recommend that you connect to the default Master Discoverer Server machine to confirm that the default installation is functioning correctly.

1. Start a Web browser on a client machine.

2. Connect to the default Master Discoverer Server by typing the following URL:

   http://hostname.domain/discoverer4i/viewer
   
   

   where hostname.domain is the fully qualified name of the machine on which Oracle9i Application Server has been installed.

   The Discoverer Viewer login screen appears when the default installation is functioning correctly.

3.2.2 Confirming the name of the Master Discoverer Server machine

During installation, the machine name is used as the Master Discoverer Server instance name. Make a note of the name of the Master Discoverer Server machine now because you will need it when installing on the machines that will become Additional Discoverer Server machines.

If you are not sure of the Master Discoverer Server machine name, follow the instructions below:

1. From the Windows Start menu on the Master Discoverer Server machine, select Run.

2. In the Run window, type regedit and press [Enter].

3. In the Registry Editor, open the HKEY_LOCAL_MACHINE/SOFTWARE/ORACLE/ key.

   The value of the DCW4_INSTANCE_NAME string is the Master Discoverer Server machine name.

3.2.3 Installing Discoverer on Additional Discoverer Server machines

On every machine that you want to make an Additional Discoverer Server machine:

1. Follow the instructions in the Oracle9i Application Server Installation Guide to install Oracle 9i Application Server on the machine you want to use as the Additional Discoverer Server machine.

2. From the Windows Start menu on the Additional Discoverer Server machine:
   1. Choose Programs | Oracle Discoverer Server 4i Setup | Unregister Preferences.

   2. Choose Programs | Oracle Discoverer Server 4i Setup | Unregister Collector.

   3. Choose Programs | Oracle Discoverer Server 4i Setup | Unregister Session.

3. From the Windows Start menu on the Additional Discoverer Server machine, select Run.

4. In the Run window, type regedit and press [Enter].

5. In the Registry Editor, open the HKEY_LOCAL_MACHINE/SOFTWARE/ORACLE/ key.

6. Change the values of the following strings as shown:

   String	Change value from:	Change value to:
   DCW4_START_LOCATOR	1	0
   DCW4_INSTANCE_NAME	Additional Discoverer Server machine name	Master Discoverer Server machine name (see Section 3.2.2, "Confirming the name of the Master Discoverer Server machine")
   DCW4_OADPORT	The current port number	The same value as the value that this string has on the Master Discoverer Server machine

   Note that you will need to open the Registry Editor on the Master Discoverer Server machine to find out the value of the DCW4_OADPORT on that machine.

7. On the Master Discoverer Server machine:
   1. From the Windows Start menu, choose Settings | Control Panel and double-click on the Services icon to display the Services dialog box.

   2. Select the OracleDiscoverer4i service in the Services dialog box and click the Stop button.

   3. Select the OracleiAS_HomeHTTPServer service in the Services dialog box and click the Stop button.

   4. Close the Services dialog box.

8. On the Additional Discoverer Server machine:
   1. From the Windows Start menu, choose Settings | Control Panel and double-click on the Services icon to display the Services dialog box.

   2. Select the OracleDiscoverer4i service in the Services dialog box and click the Stop button.

   3. Select the OracleiAS_HomeHTTPServer service in the Services dialog box and click the Stop button.

   4. Select the OracleiAS_HomeHTTPServer service in the Services dialog box, click the the Startup button to display the Service dialog box, and select Manual as the Startup Type.

   5. Click OK to close the Service dialog box.

   6. Close Close to close the Services dialog box.

9. On both the Master Discoverer Server machine and the Additional Discoverer Server machine, stop any Discoverer processes that are currently running as follows:
   1. Display the Windows Task Manager (by pressing Ctrl-Alt-Del and clicking the Task Manager button).

   2. Select any of the following Discoverer processes if they appear on the Processes tab and click End Process:

      dis4ws.exe

      dis4pr.exe

      dis4srv.exe

   3. Close the Windows Task Manager.

10. Copy the following directory (and all its subdirectories) from the Master Discoverer Server machine to the Additional Discoverer Server machine:

    <ORACLE_806_HOME>\discwb4\

    where <ORACLE_806_HOME> is the location in which the Discoverer Components are installed.

    You can copy the discwb4 directory (and all its subdirectories) in a number of different ways. For example, you could use Windows Explorer to map a network drive on the Additional Discoverer Server machine to the appropriate drive on the Master Discoverer Server machine. Alternatively, you could use FTP software to copy the files.

11. Reboot the Master Discoverer Server machine.

12. Reboot the Additional Discoverer Server machine.

13. On the Additional Discoverer Server machine, choose Programs | Oracle Discoverer Server 4i Setup | Register Session from the Windows Start menu.

    Some menu items and batch files are installed on the Additional Discoverer Server machine that are not required. We strongly recommend that you remove these menu items and batch files to prevent Discoverer Services components being inadvertently accessed.

14. To remove unnecessary Discoverer Services menu items from the Additional Discoverer Server machine:
    1. Right click on the Windows Start menu button and select Explore All Users to display Windows Explorer.

    2. Open the Start Menu\Programs\Oracle Discoverer Server 4i Setup directory.

    3. Delete the following menu items:

       Apply Preferences

       Edit Preferences

       Register Collector

       Register Preferences

       Unregister Collector

       Unregister Preferences

    4. Close Windows Explorer.

15. To remove unnecessary Discoverer Services batch files from the Additional Discoverer Server machine:
    1. Open Windows Explorer and navigate to the following directory:

       <ORACLE_806_HOME>\discwb4\util

       where <ORACLE_806_HOME> is the location in which the Discoverer Components are installed.

    2. Delete the following batch files:

       RegisterCollector.bat

       RegisterPreference.bat

       StartLocator.bat

       unRegisterCollector.bat

       unRegisterPreference.bat

When you have installed Discoverer on every machine that you want to be an Additional Discoverer Server machine, you must:

• edit the pref.txt file on the Master Discoverer Server machine (Discoverer Plus and Viewer - see Section 3.2.4)

• edit the tnsnames.ora file on all Discoverer Server machines (Discoverer Plus and Viewer - see Section 3.2.5)

• edit the disco4iv.xml file on the Master Discoverer Server machine (Discoverer Viewer only - see Section 3.2.6)

3.2.4 Editing the Discoverer Services pref.txt file (Discoverer Plus and Viewer)

3.2.4.1 What is the pref.txt file?

The pref.txt file located on the Master Discoverer Server contains a number of default settings that apply to all end users.

The only information required in the pref.txt file is the IP addresses (or machine names) of the machines used for Oracle9iAS Discoverer. The other items in the pref.txt file can be edited to suit your network or user requirements. See Section 3.2.4.5, "How to edit the pref.txt file" for more information.

A backup copy of pref.txt is located at <ORACLE_806_HOME>\discwb4\util\defaults.txt on the Master Discoverer Server machine. If you make a mistake when editing, lose, or corrupt the pref.txt file, you can restore the file to its default values from the backup copy.

3.2.4.2 Why edit the pref.txt file?

In a distributed Discoverer installation, the pref.txt file located on the Master Discoverer Server must contain either the IP address or machine name of each Application Server machine that will run Oracle9iAS Discoverer sessions.

The order of the IP addresses listed in the pref.txt file determines the order in which sessions are started on each machine that has a Session component installed. Editing the pref.txt file enables you to add Additional Discoverer Server machines and to balance the load between them.

Entries in the pref.txt file are comma space delimited (i.e. entries are separated by a comma followed by a space). Enclose the entries in "double quotes."

Note: Using IP addresses is somewhat faster because using machine names requires one extra lookup. See your System administrator for details about using IP addresses versus machine names.

3.2.4.3 What is load balancing?

Load balancing is a way to improve the performance of your Discoverer installation by distributing sessions amongst different machines to make the most efficient use of each machine. You specify the machines to use by including their IP addresses (or machine names) in the pref.txt file.

The Discoverer Services Locator component uses the list of machines in the pref.txt file to determine which machine starts the next requested session. Using a round-robin method, the Locator requests a session on each machine in order, until it reaches the end of the list of IP addresses. When the Locator reaches the end of the list, it returns to the beginning of the list and starts over.

This round-robin method enables you to balance the load placed on the machines by:

• listing the machines in a particular order

• including the same machine several times

For example, you may want one machine to handle five sessions before the next machine is used. If so, include the first machine's IP address five times before including the next machine's address in the pref.txt file

Load balancing can greatly affect performance. We recommend that you plan a load balancing strategy before editing the pref.txt file. Consider the speed and performance of each server machine. For planning purposes, you can estimate that each session requires approximately 3.8 to 18 MB of memory.

3.2.4.4 Examples of Load Balancing

Example 1: Load balancing - equal machines

You have Discoverer Session components installed on two Application Server machines. Each machine has the same processor speed and RAM. The IP addresses for these two machines are:

Table 3-1 Sample Server Names

Server	Machine Name	IP address
App Server machine 1	disco1	123.456.789.1
App Server machine 2	disco2	123.456.789.2

You want App Server machine 1 to handle the first request, App Server machine 2 to handle the next, App Server machine 1 the next, and so on.

The pref.txt file entry would look like this:

Machine IPs="disco1, disco2"

or

Machine IPs="123.456.789.1, 123.456.789.2"

Example 2: Load balancing - one fast machine plus two other machines

You have Discoverer Sessions installed on three Application Server machines. The first Application Server machine has faster processors and more RAM. The second and third Application server machines are equal to each other in processor speed and RAM.

The IP addresses for these three machines are:

Table 3-2 Sample Server Names

Server	Machine Name	IP address
App Server machine 1	serve1	123.456.789.1
App Server machine 2	serve2	123.456.789.2
App Server machine 3	serve3	123.456.789.3

You want App Server machine 1 to handle the first three requests, App Server machine 2 to handle next one, App Server machine 3 the next one, then back to App Server machine 1 for the next three requests.

The pref.txt file entry would look like this:

Machine IPs="serve1, serve1,serve1, serve2, serve3"

or

Machine IPs="123.456.789.1,123.456.789.1,123.456.789.1, 123.456.789.2, 123.456.789.3"

3.2.4.5 How to edit the pref.txt file

You edit the pref.txt file on the machine where you installed the Preferences component (i.e. the Master Discoverer Server machine):

1. From the Windows Start menu, choose Programs | Oracle Discoverer Server 4i Setup | Edit Preferences.

   
   

   The file, Prefs.txt, opens in the Notepad application.

   
   
2. Type the IP address or machine name for each machine at the line labeled MachineIPs near the top of the file.

3. Separate each IP address or machine name with a comma followed by a space and enclose the entire list in "double quotes."

   For example: "server1, server2, server3".

4. When you're finished editing the pref.txt file, save it and exit Notepad.

   For the changes you have made to pref.txt to take effect, you must apply preferences.

5. From the Windows Start menu, choose Programs | Oracle Discoverer Server 4i Setup | Apply Preferences.

   A confirmation window shows that the new preferences have been saved.

   
   

   If errors are detected in the pref.txt file, the confirmation window file includes an instruction to check the error.txt file. Correct any errors listed in the error.txt file and reapply preferences before continuing.

6. To continue, press Enter.

The preferences are updated in the Windows NT Registry. Preferences are now set for the Discoverer Server Instance.

3.2.5 Editing the tnsnames.ora file (Discoverer Plus and Viewer)

3.2.5.1 What is the tnsnames.ora file?

The tnsnames.ora file contains the names and aliases of all the databases that users can access using Oracle9iAS Discoverer or any other Oracle product.

3.2.5.2 Why edit the tnsnames.ora file?

Each server machine in a distributed Discoverer installation must have an identical tnsnames.ora file.

If you have installed Discoverer on an Additional Discoverer Server machine, you must make sure the tnsnames.ora files on the different machines are identical by doing one of the following

• copy the tnsnames.ora file from the Master Discoverer Server machine to each Additional Discoverer Server machine

• edit the tnsnames.ora file on each Additional Discoverer Server so that it is identical to the tnsnames.ora file on the Master Discoverer Server machine

Note that several versions of the tnsnames.ora file might exist on the same machine. It is very important that you copy or edit the correct file.

3.2.5.3 How to copy the tnsnames.ora file

1. Copy the tnsnames.ora file from the following location on the Master Discoverer Server machine to the same location on the Additional Discoverer Server machine and replacing the existing file:

   <ORACLE_806_HOME>\net80\admin

   where <ORACLE_806_HOME> is the location in which the Discoverer Components are installed.

   You can copy the tnsnames.ora file in a number of different ways. For example, you could use Windows Explorer to map a network drive on the Additional Discoverer Server machine to the appropriate drive on the Master Discoverer Server machine. Alternatively, you could use FTP software to copy the file.

3.2.5.4 How to edit the tnsnames.ora file

One way to edit the tnsnames.ora file:

1. From the Windows Start menu, choose Programs | Oracle for Windows NT - Oracle_806| Oracle Net8 Easy Config.

   A program then runs so you can edit the Net8 configuration.

   To make sure that you edit the correct tnsnames.ora file, do not use the Net8 Configuration Assistant (accessible from Programs | Oracle - iSuites | Network Administration).

3.2.6 Editing the disco4iv.xml file (Discoverer Viewer only)

3.2.6.1 What is the disco4iv.xml file?

The disco4iv.xml file on the Master Discoverer Server machine provides Discoverer Viewer with configuration information. Among other things, Discoverer Viewer uses the disco4iv.xml file to identify the Master Discoverer Server machine.

3.2.6.2 Why edit the disco4iv.xml file?

When you install Discoverer Viewer on multiple machines, you need to modify the disco4iv.xml file to identify the Master Discoverer Server.

3.2.6.3 How to edit the disco4iv.xml file and what to change

Before editing the disco4iv.xml file, we strongly recommend that you take a copy of the file for future reference.

1. Use Notepad to open the disco4iv.xml file in the following location on the Master Discoverer Server machine:

   <iSUITES_HOME>\apache\apache\htdocs\disco4iv\html

   where <iSUITES_HOME> is the location in which Oracle9i Application Server components are installed.

2. Confirm that the session name entry in the disco4iv.xml file is as follows:

   session name="instance_nameOracleDiscovererSession4"
   
   

   where instance_name is the Master Discoverer Server instance name.

3. Confirm that the locator name entry in the disco4iv.xml file is as follows:

   locator name="instance_nameOracleDiscovererLocator4"
   
   

   where instance_name is the Master Discoverer Server instance name.

4. Change the path entry in the disco4iv.xml file

   change from:	path="http://%LOCATOR_URL%"
   change to:	path="http://locator_location"
   where:	locator_location is the location of the locator.ior file
   example:	path="http://machinename.oracle.com/discwb4/Applet/"

5. Remove the following two lines in the disco4iv.xml file:

   <!-- REMOVE THIS COMMENT LINE (A) only if Discoverer 4i Viewer is installed on a different subnet 
   than the Discoverer Services, or you are performing a distributed Discoverer Services 
   installation
   
   REMOVE THIS COMMENT LINE (B) only if Discoverer 4i Viewer is installed on a different subnet than 
   the Discoverer Services, or you are performing a distributed Discoverer Services installation-->
   
   

6. Save the file and exit Notepad.

   For the changes you have made to the disco4iv.xml file to take effect, you must restart two Windows NT services on the Master Discoverer Server machine.

7. From the Windows Start menu, choose Settings | Control Panel and double-click on the Services icon.

   The Services dialog box appears.

   
   

8. Select the OracleDiscoverer4i service in the dialog box and click the Stop button.

9. Select the OracleiAS_HomeHTTPServer service in the dialog box and click the Stop button.

10. Wait for several seconds to make sure the service has stopped.

11. Select the OracleDiscoverer4i service in the dialog box and click the Start button.

12. Select the OracleiAS_HomeHTTPServer service in the dialog box and click the Start button.

13. Close the Services dialog box.

3.2.7 Confirming connection to the Additional Discoverer Server

To confirm that the creation of Additional Discoverer Server machines has been successful, we recommend that you connect to each Additional Discoverer Server machine as follows:

1. On each Additional Discoverer Server machine, display the Windows Task Manager (by pressing Ctrl-Alt-Del and clicking the Task Manager button) and display the Processes tab.

2. Start a Web browser on a client machine.

3. Connect to the Master Discoverer Server machine by typing the following URL:

   http://hostname.domain/discoverer4i/viewer
   
   

   where hostname.domain is the fully qualified name of the Master Discoverer Server machine.

   A process starts on the first Additional Discoverer Server machine specified in the pref.txt file and the Discoverer Viewer login screen appears.

4. To confirm that the installation was successful, look for a process called dis4ws.exe that starts on the first Additional Discoverer Server machine.

5. Repeat the above steps for each Additional Discoverer Server machine specified in the pref.txt file.