5
Installing OracleAS Discoverer in a multiple machine environment

5.1 Installing OracleAS Discoverer in a multiple machine environment

This chapter explains how to configure OracleAS Discoverer in a multiple machine environment, and contains the following topics:

• Section 5.2, "What is a multiple machine Discoverer environment?"

• Section 5.3, "About OracleAS installations"

• Section 5.4, "What are the pre-requisites for using OracleAS Web Cache to provide load balancing for OracleAS Discoverer"

• Section 5.5, "About using OracleAS Web Cache Manager to configure load balancing for OracleAS Discoverer"

• Section 5.6, "How to deploy OracleAS Discoverer with load balancing using OracleAS Web Cache"

• Section 5.7, "About the Discoverer Preferences component in a multiple machine environment"

• Section 5.8, "About configuring the tnsnames.ora file in a multiple machine environment"

5.2 What is a multiple machine Discoverer environment?

A multiple machine Discoverer environment is a Discoverer deployment that contains two or more machines running OracleAS Discoverer.

A typical multiple machine Discoverer environment uses a standard commercial hardware router to distribute Discoverer Web traffic to other Discoverer machines. This is commonly known as load balancing.

However, you can also provide load balancing using OracleAS Web Cache as a proxy server to distribute Discoverer Web traffic to other Discoverer machines.

Load balancing improves OracleAS Discoverer's performance, scalability, and availability.

Text description of the illustration multi3.gif

In the diagram above, OracleAS Web Cache on machine_a (URL http://company.machine_a.com) distributes Discoverer Web traffic to machine_b (http://company.machine_b.com) and machine_c (http://company.machine_b.com). In other words, you can have a single Discoverer URL for multiple Discoverer machines.

For more information about using OracleAS Web Cache to load balance, see Section 5.6.2, "How to configure OracleAS Web Cache for load balancing".

Notes

• There are two other types of multiple machine environment:
  • load balanced with high availability - this configuration provides load balancing with additional support for failure detection and failover of OracleAS Web Cache servers. For more information about implementing high availability, see Oracle Application Server Web Cache Administration and Deployment Guide.

  • non-load balanced - this configuration is essentially a number of unconnected OracleAS Discoverer machines that operate independently. In other words, you have a different Discoverer URL for each machine. For example, you might deploy Discoverer Plus on one machine and Discoverer Viewer on another machine.

• When you deploy OracleAS Discoverer across multiple machines with load balancing, you also provide load balancing for other OracleAS components on those machines. For example, you can also deploy OracleAS Portal with load balancing.

• To provide a consistent Discoverer interface to end users, when you deploy OracleAS Discoverer across multiple machines with load balancing, make sure that each machine has the same configuration settings (e.g user interface customizations, timeouts).

5.3 About OracleAS installations

Before you can deploy OracleAS Discoverer on multiple machines, you need a basic understanding of OracleAS Discoverer installations (if you are already familiar with OracleAS installations, skip to Section 5.4, "What are the pre-requisites for using OracleAS Web Cache to provide load balancing for OracleAS Discoverer").

A typical OracleAS Discoverer installation comprises the following:

• one OracleAS infrastructure installation, containing the underlying database, directory server, and management servers necessary for OracleAS middle tier components

  Note: There is one OracleAS infrastructure installation per OracleAS farm.

• one or more OracleAS Business Intelligence and Forms type installations, one per machine

• (optional) one OracleAS J2EE and Web Cache type installation on one machine, to enable OracleAS Web Cache to act as a proxy machine (i.e. if you are not using a standard commercial hardware router or load balancer)

An OracleAS instance is a single OracleAS installation in one Oracle home. For example, an OracleAS Business Intelligence and Forms type installation.

You can have more than one instance on one machine. For example, you might have one OracleAS infrastructure installation and one OracleAS Business Intelligence and Forms type installation on the same machine, but in different Oracle homes. For more information, see Section 5.3.1, "About installing Discoverer on a single machine".

Notes

• 'Business Intelligence and Forms' and 'J2EE and Web Cache' are types of OracleAS installation. For more information, see Oracle Application Server Installation Guide.

• A machine can only have one OracleAS infrastructure installation.

• A machine can have multiple Business Intelligence and Forms installations.

5.3.1 About installing Discoverer on a single machine

When Discoverer is deployed on a single machine, the OracleAS infrastructure installation and the OracleAS Business Intelligence and Forms type installation are located on the same machine but in separate Oracle homes (see diagram below).

Figure 5-1 Installing OracleAS Discoverer on a single machine

Text description of the illustration infra1.gif

5.3.2 About installing Discoverer on multiple machines

When Discoverer is deployed on multiple machines, the OracleAS infrastructure installation and an OracleAS Business Intelligence and Forms type installation are typically installed on one machine, and one or more OracleAS Business Intelligence and Forms type installations are installed on other machines. These standalone OracleAS components are typically linked together in an OracleAS farm.

Note: An OracleAS farm is a collection of OracleAS instances that share the same OracleAS infrastructure instance.

In the diagram below, OracleAS machine_a contains the OracleAS infrastructure installation and an OracleAS Business Intelligence and Forms type installation. OracleAS machine_b and OracleAS machine_c contain OracleAS Business Intelligence and Forms type installations. The three machines are linked together in an OracleAS farm.

Figure 5-2 Installing OracleAS Discoverer on multiple machines

Text description of the illustration infra2.gif

You might use OracleAS Web Cache as a proxy server to distribute Discoverer Web server requests to other Discoverer machines in an OracleAS farm. For more information about using OracleAS Web Cache to load balance, see Section 5.6.2, "How to configure OracleAS Web Cache for load balancing".

5.3.3 About using Application Server Control to manage multiple machines

When you choose the OracleAS installation type during installation and select the Business Intelligence and Forms option, OracleAS Discoverer is installed on that machine. You can subsequently install a Business Intelligence and Forms instance on other machines and link instances together in an OracleAS farm.

For example, you might have installed the following:

• one OracleAS infrastructure installation on host 1 (e.g. in /home/ias/infrastructure)

• one OracleAS Business Intelligence and Forms type installation on host 1 (e.g. in /home/ias/Discoverer)

• one OracleAS Business Intelligence and Forms type installation on host 2 (e.g. in /home/ias/Discoverer)

You use Application Server Control to manage OracleAS farms. The screen below shows how the above scenario is represented in Application Server Control. Each machine is represented as a row in the Standalone Instances table.

Text description of the illustration cluster2.gif

Notes

• For more information about using Application Server Control to manage OracleAS farms, refer to the Application Server Control Help.

• When OracleAS Discoverer is installed on multiple machines, the Discoverer Preferences component is installed on each machine, but only one Preferences component is used (for more information, see Section 1.10.2.2, "What is the Discoverer Preferences component?" and Section 5.7, "About the Discoverer Preferences component in a multiple machine environment")

5.4 What are the pre-requisites for using OracleAS Web Cache to provide load balancing for OracleAS Discoverer

Before you can configure OracleAS Discoverer for load balancing using OracleAS Web Cache, you must have the following installed:

• an OracleAS infrastructure instance

• two or more OracleAS Business Intelligence and Forms type instances on different machines (note that OracleAS Web Cache is also installed as part of an OracleAS Business Intelligence and Forms type installation)

• (optional) one OracleAS J2EE and Web Cache type instance on one machine

Notes

• You can either install OracleAS Web Cache as part of an OracleAS Business Intelligence and Forms type installation or as part of an OracleAS J2EE and Web Cache type installation. Choose an installation type as follows:
  • use the Business Intelligence and Forms type installation if you want to run OracleAS Discoverer and OracleAS Web Cache on the same machine

  • use the J2EE and Web Cache type installation if you only want to run OracleAS Web Cache on that machine

• It is recommended that you put the OracleAS Discoverer instances (i.e. that you are using to provide load balancing) in the same OracleAS farm.

• If OracleAS Web Cache is installed on a separate instance, it does not have to be part of the same farm as the OracleAS Discoverer instances.

5.5 About using OracleAS Web Cache Manager to configure load balancing for OracleAS Discoverer

You can use OracleAS Web Cache Manager to configure load balancing for OracleAS Discoverer across multiple machines. For example, you might have the following:

• three machines in an OracleAS farm - machine_a, machine_b, and machine_c

• OracleAS Web Cache is running on machine_a

• OracleAS Discoverer running on machine_b and machine_c

  Note: OracleAS Web Cache might also be running on machine_b and machine_c but is not used to load balance the machines.

Configuring OracleAS Web Cache for load balancing involves the following tasks:

• choose which machine you want to specify as the proxy machine and start OracleAS Web Cache Manager on that machine

• define the OracleAS Discoverer machines that you want to use to provide load balancing (using the Origin Servers page in OracleAS Web Cache Manager),

• define the load balancing relationship between OracleAS Web Cache and the OracleAS Discoverer instances (using the OracleAS Web Cache Site to Server Mapping page in OracleAS Web Cache Manager)

• enable the Default Session Binding option (using the Session Binding page in OracleAS Web Cache Manager)

• restart OracleAS Web Cache (using the Cache Operations page in OracleAS Web Cache Manager)

For more information about using OracleAS Web Cache Manager to provide load balancing with OracleAS Discoverer, see Section 5.6.2, "How to configure OracleAS Web Cache for load balancing".

5.6 How to deploy OracleAS Discoverer with load balancing using OracleAS Web Cache

You deploy OracleAS Discoverer with load balancing to increase the number of supported Discoverer end users and improve Discoverer performance.

To deploy OracleAS Discoverer with load balancing using OracleAS, do the following:

1. On each machine that you want to use to load balance Discoverer, make sure that OracleAS Web Cache is turned on (i.e. the 'webcache' attribute of the Discoverer configuration element in configuration.xml is set to 'true'). For more information, see Section 6.7, "How to turn on OracleAS Web Cache".

   Note: Turned on does not necessarily mean that OracleAS Web Cache is running (i.e. OracleAS Web Cache is set to UP in Application Server Control). When you do an OracleAS install, OracleAS Web Cache is turned off by default (i.e. the 'webcache' attribute of the Discoverer configuration element in configuration.xml is set to 'false').

2. If you have not already created an OracleAS farm, use Application Server Control to create a new farm (for more information, see Oracle Enterprise Manager Help).

3. Use Application Server Control to add OracleAS Discoverer instances to a farm (for more information, see Application Server Control Help).

   Hint: Make sure that you can run Discoverer directly from a machine before trying to load balance to that machine. For example, if you want to load balance OracleAS Discoverer installed on machine_b, start a Web browser and enter the Discoverer URL for that machine (e.g. http://machine_b:7779/discoverer/viewer) to make sure that Discoverer works correctly.

4. Start OracleAS Web Cache Manager on the machine that you want to specify as the proxy machine (for more information, see Section 5.6.1, "How to start OracleAS Web Cache Manager").

5. Configure OracleAS Web Cache Manager to act as a proxy machine to direct Discoverer Web server requests to other Discoverer machines (for more information, see Section 5.6.2, "How to configure OracleAS Web Cache for load balancing")

6. Confirm that Discoverer Web traffic is being routed correctly (for more information, see Section 5.6.3, "How to verify that OracleAS Web Cache is configured correctly for load balancing".

7. (optional) You might want to deploy a single centralized Discoverer Preferences component (for more information, see Section 5.7, "About the Discoverer Preferences component in a multiple machine environment").

8. (optional) You might need to make sure that the tnsnames.ora file on each machine contains the same database names and aliases information (for more information, see Section 5.8, "About configuring the tnsnames.ora file in a multiple machine environment").

5.6.1 How to start OracleAS Web Cache Manager

You start OracleAS Web Cache Manager on a machine when you want to configure and monitor OracleAS Web Cache on that machine. For example, you might want to configure a machine as a proxy machine to route OracleAS Discoverer Web traffic to multiple machines.

To start OracleAS Web Cache Manager:

1. Start a Web browser.

2. Enter the OracleAS Web Cache Manager URL for the machine on which you are running OracleAS Web Cache using the fully qualified host name and domain used by your installation.

   For example:

   http://<host.domain>:4000/Webcacheadmin

   Note: The default port number for OracleAS Web Cache is 4000. You can obtain the port number from the OracleAS Ports page (for more information, see Section 4.10, "How to list ports used by OracleAS").

   The Enter Network Password page is displayed.

3. Enter an OracleAS Web Cache Manager user name (i.e. 'administrator' or a user name with administrator privileges) and network password to display the OracleAS Web Cache - Cache Operations page.

   
   
   Text description of the illustration mm5.gif

You can now configure OracleAS Web Cache for load balancing (for more information, see Section 5.6.2, "How to configure OracleAS Web Cache for load balancing").

5.6.2 How to configure OracleAS Web Cache for load balancing

You can use OracleAS Web Cache Manager to configure load balancing for Web applications such as OracleAS Discoverer. OracleAS Web Cache Manager has pages for each aspect of OracleAS Web Cache that you can configure.

For example, the Origin Servers page in the Origin Servers, Sites, and Load Balancing area enables you to specify which machines you want to use to provide load balancing for a Web application.

Note: Before you start, make sure you have the necessary OracleAS components installed (for more information, see Section 5.4, "What are the pre-requisites for using OracleAS Web Cache to provide load balancing for OracleAS Discoverer").

To configure OracleAS Web Cache for load balancing:

1. Start OracleAS Web Cache Manager (for more information, see Section 5.6.1, "How to start OracleAS Web Cache Manager").

2. Select the Origin Servers link in the Origin Servers, Sites, and Load Balancing area of the Navigator Pane to display the Origin Servers page.

   
   
   Text description of the illustration mm6.gif

   Note: You select the Origin Servers link in OracleAS Web Cache Manager, not Application Server Control.

   You use the Origin Servers page to specify and manage the OracleAS machines that you want to use to provide load balancing. For example, if you want to use OracleAS Discoverer installed on machine_b and machine_c, you need to add entries for machine_b and machine_c to the Application Web Servers table.

3. For each OracleAS Discoverer machine on which you want to load balance, do the following:
   1. Click Add... beneath the Application Web Servers table to display the Add Application Web Server page.

      
      
      Text description of the illustration mm13.gif

   2. Enter the fully qualified hostname of the machine (e.g. machine_b.company.com) in the Hostname field.

   3. Enter the OracleAS Web Cache HTTP Listen port number of the machine into the Port field, as follows:
      • for HTTP communication, use the HTTP port on which Discoverer is deployed (typically the HTTP Listen (non-SSL) port number)

      • for HTTPS communication, use the HTTPS port on which Discoverer is deployed (typically the HTTPS Listen (non-SSL) port number)

        Note: You can obtain these port numbers from the OracleAS Ports page (for more information, see Section 4.10, "How to list ports used by OracleAS").

        Hint: Display the portlist page for the Discoverer BI and Forms installation, not the OracleAS infrastructure installation.

   4. Type 50 into the Capacity field (recommended setting).

      Note: For more information about specifying the capacity, see Oracle Application Server Web Cache Administration and Deployment Guide.

   5. Type 5 into the Threshold field (recommended setting).

   6. Type / in the Ping URL field (recommended setting).

   7. Type 10 in the Ping Interval field (recommended setting).

      Note: You might want to fine tune OracleAS Web Cache later if necessary. For more information about the Create Application Web Server page, see OracleAS Web Cache Help. For more information about specifying Origin Servers, see Oracle Application Server Web Cache Administration and Deployment Guide.

   8. Select the communication protocol used by the machine from the Protocol drop down list.

      Note: If you are using the OracleAS Web Cache HTTP Listen (non-SSL) port, select HTTP. If you are using the OracleAS Web Cache HTTPS Listen (SSL) port, select HTTPS.

   9. Click Submit to save the details and display the Origin Servers page.

   Having defined the OracleAS machines that you want to load balance, you now define the load balancing relationship between OracleAS Web Cache and the OracleAS machines. For example, you might want to specify that machine_a directs Discoverer Web server requests to machine_b and machine_c.

4. Select the Site to Server Mapping link in the Origin Servers, Sites, and Load Balancing area of the Navigator Pane to display the Site to Server Mapping page.

   
   
   Text description of the illustration mm7.gif

   The Site to Server Mapping page has an entry for the machine on which you are running OracleAS Web Cache. For example, if you are running OracleAS Web Cache on machine_a, you will see a row for machine_a with default settings.

   Hint: The Port Number field under the Enter Site Name area should contain the OracleAS Web Cache listening port number that is displayed on the Listening Ports page in the Ports area.

   The next step is to specify which OracleAS Discoverer machines you want to load balance.

5. In the Select column, select the radio button next to the OracleAS Web Cache machine.

6. Click Edit Selected... to display the Edit/Add Site to Server Mapping page.

   
   
   Text description of the illustration mm8.gif

7. In the Select Application Web Servers area, select the check box next to each OracleAS Discoverer machine on which you want to provide load balancing.

   You should see the machines that you defined in the Application Web Servers table on the Origin Servers page.

   For example, if you have installed OracleAS Discoverer on machine_b and machine_c, select the check boxes next to machine_b and machine_c.

8. Click Submit to save the details and display the Site to Server Mapping page.

   The next step is to specify the session binding value, which specifies how a user session is bound to a particular application Web server.

9. Select the Session Binding link in the Origin Servers, Sites, and Load Balancing area of the Navigator Pane to display the Session Binding page.

10. In the Select column, select the radio button next to the row that contains the Default Session Binding option in the Site Name column.

    
    
    Text description of the illustration mm12.gif

11. Click Edit Selected to display the Change/Add Session Binding page.

    
    
    Text description of the illustration mm10.gif

12. Select JSESSIONID from the Default Session Binding drop down list.

13. Type 30 in the Inactivity Timeout field (recommended setting).

14. Click Submit to save the details and display the OracleAS Web Cache page.

    The next step is to apply the changes you have made and restart OracleAS Web Cache.

15. Click Apply Changes at the top of the OracleAS Web Cache page to display the Cache Operations page.

16. Click Restart.

    When OracleAS Web Cache has restarted, the Success page is displayed.

    You can now verify that browser sessions connecting to the OracleAS Web Cache machine are routed to one of the OracleAS Discoverer machines specified for load balance. For more information, see Section 5.6.3, "How to verify that OracleAS Web Cache is configured correctly for load balancing".

    Hint: If the changes that you apply are not accepted, you might find that the capacity that you have defined on one or more of the load balancing machines is too high. For example, when you click Restart you might get an error message similar to the following:

    opmnctl: stopping opmn managed processes... opmnctl: starting opmn managed processes... Request failure: 0 of 1 processes started.

    To change the capacity value of load balanced machines:

    1. Display the Origin Servers page.

    2. In the Select column, select the radio button next to the machine(s) on which you want to load balance.

    3. Click Edit Selected to display the Edit Application Web Server page.

    4. Change the value in the Capacity field to a smaller value.

    5. Click Submit.

    6. Click Apply Changes.

    7. Click Restart.

    Notes

    • For more information about using OracleAS Web Cache Manager, see Oracle Application Server Web Cache Administration and Deployment Guide.

5.6.3 How to verify that OracleAS Web Cache is configured correctly for load balancing

You can verify that OracleAS Web Cache is configured correctly for load balancing by confirming that OracleAS Discoverer Web traffic is being routed to the correct machines.

For example, you might want to confirm that Discoverer browser sessions connecting to:

http://machine_a.company.com:7777/discoverer/viewer

are routed to:

http://machine_b.company.com:7778/discoverer/viewer

Or

http://machine_c.company.com:7778/discoverer/viewer

To verify that OracleAS Web Cache is configured correctly for load balancing:

1. Start OracleAS Web Cache Manager (for more information, see Section 5.6.1, "How to start OracleAS Web Cache Manager").

2. Select the Origin Server Statistics link in the Monitoring area of the Navigator Pane to display the Origin Server Statistics page.

   
   
   Text description of the illustration mm11.gif

3. Verify the status of the OracleAS Discoverer machines to which you are distributing Discoverer Web traffic by confirming that:
   • the Origin Server Statistics table contains a row for each OracleAS Discoverer machine

     For example, if you have Discoverer sessions running on machine_a and machine_b, the Origin Server Statistics will contain a row for machine_a and a row for machine_b.

   • the application server port number is correct in the hostname column

   • the up/down setting in the Up/Down Time column setting is UP

   • the Active Sessions values should correctly reflect the number of OracleAS Discoverer sessions that are running on each machine

     For example, if you have ten Discoverer sessions running on machine_a and machine_b, the Active Sessions-now column might contain the value 6 for machine_a and the value 4 for machine_b (i.e. ten sessions in total).

   • the Active Sessions values should indicate an even distribution of server requests between the OracleAS Discoverer machines (i.e. according to how you have configured each machine in the Origin Servers page)

     For example, if you have 100 Discoverer sessions running on machine_a and machine_b, the Active Sessions-now column might should reflect a similar number of sessions for each machine.

   Notes

   • For more information about using the Origin Server Statistics page, see OracleAS Web Cache Manager help.

   • You can also select the Health Monitor link in the Monitoring area of the Navigator Pane to see a summary of server requests served by the OracleAS Discoverer machines. If OracleAS Web Cache is configured correctly for load balancing, there will be an even distribution of server requests across the OracleAS Discoverer machines.

5.7 About the Discoverer Preferences component in a multiple machine environment

Each Discoverer instance includes a Discoverer Preference component. The Discoverer Preference component stores preference settings (e.g. worksheet axis style, default EUL, auto-query enable) for OracleAS Discoverer users accessing that Discoverer instance (for more information, see Section 1.10.2.2, "What is the Discoverer Preferences component?").

In a multiple machine environment, you might want to store all Discoverer end user preferences in a single location. In other words, you want to each Discoverer instance to use the same Discoverer Preference component. To store all Discoverer end user preferences in a single location, you specify a centralized Discoverer Preferences component (for more information, see Section 5.7.1, "How to specify a centralized Discoverer Preferences component").

5.7.1 How to specify a centralized Discoverer Preferences component

If you want to store all Discoverer end user preferences in a single location, you configure each Discoverer instance to use the Preferences component running on the Preference Server machine, instead of running their own Preferences component. The diagram below shows how additional Discoverer machines reference the preferences on the Preference Server machine.

Text description of the illustration mm1.gif

To specify a centralized Discoverer Preferences component, you:

• choose which machine you want to use as the Discoverer Preference Server machine, then find out the instance name of that machine (for more information, see Section 5.7.2, "How to find out the instance name of the Discoverer Preference Server machine")

• modify the register session scripts of other machines in the multiple machine environment to use the instance name of the Discoverer Preference Server machine (for more information, see Section 5.7.3, "How to modify the register session scripts of other machines in the multiple machine environment to use the Discoverer Preference Server machine")

• disable the preferences component on all machines except the Discoverer Preference Server machine (for more information, see Section 5.7.4, "How to disable the preferences component on a machine"

• make sure that the OSAgent port is the same on all machines - to obtain the OSAgent port of a machine, look at the OSAGENT_PORT value in the opmn.xml file (for more information about the location of configuration files, see Section A.2, "List of Discoverer file locations").

Notes

• If you do not configure a central Discoverer Preferences Server machine, each machine might have different preferences settings. Discoverer end users connecting to different machine might experience different Discoverer behavior according to what preference settings are specified.

5.7.2 How to find out the instance name of the Discoverer Preference Server machine

To find out the instance name of the machine that you want to run the Preferences component (i.e. to designate the Discoverer Preference Server machine):

1. On the machine that you want to designate as the Discoverer Preference Server machine, find out the instance name, as follows:
   • on UNIX, open the discwb.sh file and find out the value of the INSTANCE_NAME= command (e.g. INSTANCE_NAME=machine_a.us.company.com)

   • on Windows, open a command prompt and type set COMPUTERNAME to display the instance name

2. Make a note of the value of the instance name.

   You use the instance name value in register session scripts of other machines in the multiple machine environment.

3. Close the register session file.

You now need to modify the register session scripts of other machines in the multiple machine environment to use the instance name of the Discoverer Preference Server machine (for more information, see Section 5.7.3, "How to modify the register session scripts of other machines in the multiple machine environment to use the Discoverer Preference Server machine").

5.7.3 How to modify the register session scripts of other machines in the multiple machine environment to use the Discoverer Preference Server machine

Having identified the instance name of the machine that is going to run the Preferences component (i.e. the Discoverer Preference Server machine), you must now make sure that other machines use the Preferences component on the Discoverer Preference Server machine.

To modify the register session scripts of other machines in the multiple machine environment to use the Discoverer Preference Server machine, on every other machine in the installation do the following:

1. Stop the Discoverer service component (for more information, see Section 4.4.2, "How to stop the Discoverer Service on a machine").

2. Open the following register session file in a text editor:
   • on UNIX, open the registersession.sh file

   • on Windows, open the registersession.bat file

   To find out the location of the file, see Section A.2, "List of Discoverer file locations".

3. Locate the '-preference' command in the register session script:

   ... -a -preference -a ${INSTANCE_NAME}OracleDiscovererPreferences9
   
   

4. Replace ${INSTANCE_NAME} with the instance name of the Discoverer Preference Server machine that you noted in Section 5.7.2, "How to find out the instance name of the Discoverer Preference Server machine".

For example, if the Discoverer Preference Server machine with the instance name machine_a.us.company.com, you would change the register session script to:

... -a -preference -a machine_a.us.company.comOracleDiscovererPreferences9

Save the register session file.

Stop the Discoverer Service on that machine (for more information, see Section 4.4.2, "How to stop the Discoverer Service on a machine").

Start the Discoverer Service on that machine (for more information, see Section 4.4.1, "How to start the Discoverer Service on a machine").

You now need to disable the preferences component on all machines except the Discoverer Preference Server machine (for more information, see Section 5.7.4, "How to disable the preferences component on a machine".

5.7.4 How to disable the preferences component on a machine

When you configure Discoverer to use a single Preference Server machine in a multiple machine environment, you must disable the preferences component on all Discoverer machines except the Preferences Server machine.

To disable the preferences component on all machines except the Preference Server machine:

1. On each machine except the Preference Server machine, open the opmn.xml file in a text editor (or XML editor).

   For more information about the location of the opmn.xml file, see Section A.2, "List of Discoverer file locations").

2. Locate the Disco_PreferenceServer entry.

3. Change the Disco_PreferenceServer entry from enabled to disabled.

   For example, you might change:

   <ias-component id="Disco_PreferenceServer" status="enabled">

   to:

   <ias-component id="Disco_PreferenceServer" status="disabled">

4. Save the opmn.xml file.

5. Stop the Discoverer Service on that machine (for more information, see Section 4.4.2, "How to stop the Discoverer Service on a machine").

6. Start the Discoverer Service on that machine (for more information, see Section 4.4.1, "How to start the Discoverer Service on a machine").

To verify that Discoverer is using a single set of preferences, run Discoverer directly from a machine and check that preferences applied are those on the Discoverer Preference Server machine. For example, if the Discoverer Preference Server machine is machine_a, run Discoverer Viewer directly from machine_b and machine_c (e.g. on the URL http://machine_b.us.company.com:7779 or http://machine_b.us.company.com:7779) and verify that Discoverer applies preferences on machine_a.

5.8 About configuring the tnsnames.ora file in a multiple machine environment

The tnsnames.ora file contains the names and aliases of all the databases that users can access using OracleAS Discoverer.

Each machine in a multiple machine Discoverer installation must have the same tnsnames.ora file or must point to a centralized tnsnames.ora file (to find out the location of this file, see Section A.2, "List of Discoverer file locations").

To must make sure that the tnsnames.ora files on the different machines are the same, do one of the following:

• copy the tnsnames.ora file from an one Discoverer Web Server machine to the same location on all of the other Discoverer Web Server machines, replacing the existing file

• edit the tnsnames.ora file on each Discoverer machine so that they all contain the same database names and aliases

Hint: Several versions of the tnsnames.ora file might exist on a machine. Make sure that you use the tnsnames.ora file listed in Section A.2, "List of Discoverer file locations".