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Oracle® Fail Safe Concepts and Administration Guide
Release 3.3.1 for Windows
Part No. A96684-01
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8
Configuring Oracle Forms Load Balancer Servers for High Availability

Oracle Fail Safe provides high availability for Web-based Oracle Forms applications that take advantage of the Oracle Forms Load Balancer Server by providing a wizard to add an Oracle Forms Load Balancer Server to a group.

Oracle Fail Safe also provides a wizard to configure Oracle Forms Servers for high availability. If you intend to use the Oracle Forms Load Balancer Server, Oracle Corporation recommends that you configure the Oracle Forms Load Balancer Server for high availability rather than the Oracle Forms Server. (Chapter 9 describes how to configure an Oracle Forms Server for high availability.)

The following topics are discussed in this chapter:

Topic Reference
Introduction   Section 8.1  
Discovering Standalone Oracle Forms Load Balancer Servers   Section 8.2  
Adding Oracle Forms Load Balancer Servers to a Group   Section 8.3  
Security Requirements for Oracle Forms Load Balancer Servers   Section 8.4  
Startup Parameter Changes   Section 8.5  
Troubleshooting Problems with Oracle Forms Load Balancer Servers   Section 8.6  

8.1 Introduction

An Oracle Forms Load Balancer Server allows you to maintain a set of middle-tier computers (sometimes called a server farm) and balance the load of server traffic among these systems. Load balancing is implemented using a CGI-bin executable file that can run on any Web server with CGI support.

The Oracle Forms Load Balancer Server keeps track of all of the Oracle Forms Servers in various load-balancing sets. It tracks the status of the servers in a given set and keeps statistics indicating their loads. It is responsible for directing each Forms execution request to the least-loaded computer in the given set.

Each Oracle Forms Load Balancer Client sends load information to the Oracle Forms Load Balancer Server, such as the number of Forms processes that are currently running on the system. The Oracle Forms Load Balancer Client runs on each system with an Oracle Forms Server.

The steps that follow explain the events that occur when you use load balancing with a CGI-bin executable file:

  1. Oracle Forms Load Balancer Clients periodically send load information to the Oracle Forms Load Balancer Server. This load information includes the total number of processes running on each Oracle Forms Load Balancer Client.

  2. A user accesses a URL that points to the Forms CGI-bin executable file.

  3. The Forms CGI-bin executable file asks the Oracle Forms Load Balancer Server for the name of the least-loaded system that is available.

  4. The Forms CGI-bin executable file dynamically creates an .html file with the name of the least-loaded system specified as the system on which to run the Forms Server, and returns that .html file to the user's Web browser.

  5. The user's Web browser requests that the Java applet be downloaded from the host specified in the .html file.

  6. The Java applet sends a request to the Forms Server asking for a particular Form Builder application (an .fmx file).

  7. The server contacts a Forms Server runtime engine. (The server maintains a set of available runtime engines to minimize application startup delays.) Each active user receives a dedicated runtime engine.

  8. The server establishes a direct socket, HTTP, or HTTPS connection with the runtime engine, and sends the socket, HTTP, or HTTPS information to the Java applet. The Java applet then establishes a direct socket, HTTP, or HTTPS connection with the runtime engine. The Java applet and the runtime engine now communicate directly, freeing the server to accept startup requests from other users. (At this point, neither the application server nor the Forms Server is involved in the communication between the applet and the runtime engine.) The Java applet displays the application's user interface in the main window of the user's Web browser.

  9. The runtime engine communicates directly with the database through Oracle Net or ODBC (Open Database Connectivity), depending on the data source.

  10. Oracle Forms Load Balancer Clients continue to send load information to the Oracle Forms Load Balancer Server. All new service requests are routed based on that information.

In this way, Oracle Forms and the Oracle Forms Load Balancer Server provide highly available forms without the use of Oracle Fail Safe. However, the Oracle Forms Load Balancer Server itself can be a point of failure. If it becomes unavailable, the Oracle Forms CGI-bin executable file will not get any information back about which is the least-loaded system (in step 3 in the previous list). Instead, the Forms CGI-bin executable file will redirect the user's browser to the URL specified by the Oracle Forms Load Balancer Server MetricsServerErrorURL parameter.

By using Oracle Fail Safe to configure the Oracle Forms Load Balancer Server for high availability, you eliminate this point of failure in the configuration.

Figure 8-1 shows a multitiered implementation in which the Oracle Forms Load Balancer Server and the Oracle Web servers reside on a separate cluster from the database. The Oracle Forms Servers and the Oracle Forms Load Balancer Clients reside on several noncluster systems.

The three tiers in Figure 8-1 include:

Multitiered implementations allow for incremental deployment of high availability into your Internet business solution. For example, with Oracle Fail Safe, you can eliminate potential points of failure for the components in either the Oracle Forms Load Balancer Server or the database, or both can be configured on clusters for high availability with Oracle Fail Safe.

Figure 8-1 Three-Tiered Architecture for Forms Using the Forms Load Balancer Server

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8.2 Discovering Standalone Oracle Forms Load Balancer Servers

You configure Oracle Forms Load Balancer Servers for high availability using Oracle Fail Safe Manager. Before you can view standalone Oracle Forms Load Balancer Servers in the Oracle Fail Safe Manager interface, they must first be discovered. Oracle Services for MSCS discovers Oracle Forms Load Balancer Servers by reviewing the list in the Windows service manager, finding Oracle Forms Load Balancer Server entries, and determining which have not already been configured for high availability. Oracle Fail Safe displays the newly discovered services in the Oracle Fail Safe Manager tree view under the Standalone Resources folder.

8.3 Adding Oracle Forms Load Balancer Servers to a Group

To configure an Oracle Forms Load Balancer Server for high availability, you add it to a group. Oracle Fail Safe provides a wizard that allows you either to add an existing Oracle Forms Load Balancer Server to a group or to create and add a new Oracle Forms Load Balancer Server to a group. When you add an Oracle Forms Load Balancer Server to a group, Oracle Fail Safe adds all other resources upon which the Oracle Forms Load Balancer Server depends. Typically, the group includes the following resources:

You can make the entire Web application highly available by also adding an Oracle HTTP Server to a group and the database that the Forms Servers access to a group. The groups to which you add the Oracle Forms Load Balancer Server, the Oracle HTTP Server, and the database can be different groups.


Note:

Although the Oracle Forms Load Balancer Server itself is recovered after a failover, any form input that did not get committed to the database prior to a failover is lost. Uncommitted form input that is lost during a failover must be reentered by the user or application.

8.3.1 Before You Get Started

Before you add an Oracle Forms Load Balancer Server to a group, note the following:

  • The Oracle Forms Load Balancer Server executable files must be installed in an Oracle home on a private disk on each cluster node that is a possible owner for the Oracle Forms Load Balancer Server.

  • All other necessary Oracle product executable files must be installed in the Oracle home or homes on each cluster node that is a possible owner for the Oracle Forms Load Balancer Server.

  • The group must contain at least one virtual address.

8.3.2 Configuration Steps

Oracle Fail Safe automates the steps required to make an Oracle Forms Load Balancer Server highly available. Oracle Fail Safe can add an existing Oracle Forms Load Balancer Server to a group, or it can create a new Oracle Forms Load Balancer Server and then add it to a group.

Table 8-1 provides a quick reference to the tasks needed to configure an Oracle Forms Load Balancer Server for high availability. For step-by-step instructions about a task, refer to the Oracle Fail Safe online help. From the Oracle Fail Safe Manager menu bar, choose Help, then "Search for Help on."

Table 8-1 Steps for Configuring an Oracle Forms Load Balancer Server

Step Procedure Comments
1 Ensure that the Oracle Forms Load Balancer Server software is installed on a private disk on each node in the cluster that you intend to be a possible owner for the Oracle Forms Load Balancer Server. See the Oracle Forms documentation for installation information.
2 Invoke Oracle Fail Safe Manager. From the Windows Start menu, choose Oracle - <Oracle_Home>, then Oracle Fail Safe Manager.
3 Verify the cluster. Choose Troubleshooting, then Verify Cluster to run a procedure that validates the cluster hardware and software configurations.
4 Create a group and add one or more virtual addresses. Choose Groups, then Create to run the Create Group Wizard. The wizard helps you to set up failover and failback policies and automatically opens the Add Resource to Group Wizard to allow you to add a virtual address to the group. (Choose Resources, then Add to Group to add additional virtual addresses to the group.)
5 Add the Oracle Forms Load Balancer Server to the group. Choose Resources, then Add to Group to run the Add Resource to Group Wizard. The wizard helps you to select the Oracle Forms Load Balancer Server,Foot  specify the data port and the request port, and specify the maximum number of Oracle Forms Load Balancer Clients.
6 Verify the group. Choose Troubleshooting, then Verify Group to check for and fix any problems with the group, resources, or failover configuration.
7 Configure the Oracle HTTP Server for failover. Create and add an Oracle HTTP Server to a group to make your Oracle Forms application available on the Web. See Chapter 11 for information about creating and adding an Oracle HTTP Server to a group.
Footnote If you add an existing Oracle Forms Load Balancer Server to the group, you can select its name (from the Load Balancer Server Name box) in the Add Resource to Group Wizard. If you are creating and adding a new Oracle Forms Load Balancer Server, specify a name that is unique across the cluster.

8.3.3 Configuration Data for Oracle Forms Load Balancer Servers

Oracle Fail Safe Manager provides the Add Resource to Group Wizard to help you configure an Oracle Forms Load Balancer Server for high availability. When you use the Add Resource to Group Wizard, you need the following data:

  • Possible owner nodes for the Oracle Forms Load Balancer Server, if the cluster consists of more than two nodes, or if one node is not available in a two-node cluster

  • The virtual address with which you want to associate the Oracle Forms Load Balancer Server

  • A name that is unique across the cluster for the Oracle Forms Load Balancer Server

  • The data port on which the Oracle Forms Load Balancer Server will listen for load data from the Oracle Forms Load Balancer Clients

  • The request port on which the Oracle Forms Load Balancer Server will listen for requests for the least-loaded host made by the Forms Web CGI

  • The maximum number of Oracle Forms Load Balancer Clients that you want to access the Oracle Forms Load Balancer Server

The clusterwide operation to add an Oracle Forms Load Balancer Server to a group will fail if another cluster resource with the same name already exists.

The following sections describe in detail the data requirements for adding an Oracle Forms Load Balancer Server to a group.

8.3.3.1 Choose Nodes

If you are adding an Oracle Forms Load Balancer Server to a group and the cluster consists of more than two nodes, you are asked to specify which nodes should be possible owners for the Oracle Forms Load Balancer Server by specifying a list of selected nodes, as shown in Figure 8-2. To specify that a particular node should not be a possible owner for the Oracle Forms Load Balancer Server, select the node from the Selected Nodes list and click the left arrow.

Section 2.6.6 describes in detail the concept of the possible owner nodes list.

Figure 8-2 Choose Nodes Wizard Page When All Nodes Are Available

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If you are adding an Oracle Forms Load Balancer Server to a group and the cluster consists of two or more nodes, but one or more nodes are unavailable, you are also asked to specify which nodes should be possible owners for the Oracle Forms Load Balancer Server. In this case, the wizard page displays which nodes are unavailable and why, as shown in Figure 8-3.

Figure 8-3 Choose Nodes Wizard Page When Any Node Is Unavailable

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8.3.3.2 Oracle Forms Load Balancer Server Listener Virtual Address

A group must contain at least one virtual address before you add an Oracle Forms Load Balancer Server to it. If the group to which you are adding an Oracle Forms Load Balancer Server contains more than one virtual address, you are asked to select which one you would like to associate with the Oracle Forms Load Balancer Server, as shown in Figure 8-4.

Figure 8-4 Choose Virtual Address Wizard Page

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8.3.3.3 Oracle Forms Load Balancer Server Identity

The Add Resource to Group Wizard requests the following information about the Oracle Forms Load Balancer Server identity, as shown in Figure 8-5.

  • The Oracle Forms Load Balancer Server name

    Select an existing Oracle Forms Load Balancer Server to add an existing Load Balancer Server to the group. Enter a name that is unique across the cluster to direct Oracle Fail Safe to create a new Oracle Forms Load Balancer Server.

  • Data port

    This is the TCP/IP port number on which the Oracle Forms Load Balancer Server will listen for load data from the Oracle Forms Load Balancer Clients. Note that the data port value for the Oracle Forms Load Balancer Server must be the same as the data port value specified for all Oracle Forms Load Balancer Clients.

    The default value is 9010 if you are creating a new Oracle Forms Load Balancer Server. The default for an existing Oracle Forms Load Balancer Server is the value that was specified when the Oracle Forms Load Balancer Server software was installed. Oracle Corporation recommends that you specify a value other than the default value only if the default value (9010) is already being used by another program.

  • Request port

    This is the TCP/IP port number on which the Oracle Forms Load Balancer Server will listen for requests for the least-loaded host made by the Forms Web CGI. This value is written to the formsweb.cfg file as the MetricServerPort parameter. See the Oracle Forms documentation for details about this file.

    The default value is 9020 if you are creating a new Oracle Forms Load Balancer Server. The default for an existing Oracle Forms Load Balancer Server is the value that was specified when the Oracle Forms Load Balancer Server software was installed. Oracle Corporation recommends that you specify a value other than the default value only if the default value (9020) is already being used by another program.

  • Maximum

    This is the maximum number of Oracle Forms Load Balancer Clients that you want to access the Oracle Forms Load Balancer Server.

See Section 8.5 for important information on required startup parameters changes.

Note that the wizard does not request the value to which you want to set the trace level for the Oracle Forms Load Balancer Server. By default, Oracle Fail Safe sets the trace level for the Oracle Forms Load Balancer Server to zero (no tracing) when it creates a new concurrent manager. When you add an existing Oracle Forms Load Balancer Server to a group, Oracle Fail Safe uses the current setting of that Oracle Forms Load Balancer Server for the trace level. The trace level determines the amount of information written to the Oracle Forms Load Balancer Server trace file. To change the trace level, select the Oracle Forms Load Balancer Server from the Oracle Fail Safe tree view, then click the Parameters tab and make the desired changes.

Figure 8-5 Oracle Forms Load Balancer Server Identity Wizard Page

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8.4 Security Requirements for Oracle Forms Load Balancer Servers

The Oracle Forms Load Balancer Server does not require any special privileges to run in a cluster environment. See Section 4.3 for information about appropriate privileges to manage Oracle resources and applications and to perform operations through Oracle Fail Safe Manager.

8.5 Startup Parameter Changes

The following sections describe the changes you need to make to startup parameters so that:

In addition, Section 8.5.4 describes how to make changes to the startup parameters for the Oracle Forms Load Balancer Server after it has been made highly available.

8.5.1 Changes to Startup Parameters for Forms CGI-Bin Executable Files

To allow the Oracle Forms Server CGI-bin executable files to access the highly available Oracle Forms Load Balancer Server, make the following changes in the <Oracle_Home>\FORMS60\Server\formsweb.cfg file:

  • Adjust the MetricsServerPort parameter to match the Oracle Forms Load Balancer Server "request port" startup parameter.

  • Set the ServerHost parameter to %LeastLoadedHost%. If the domain name is required for name resolution, then append the domain name to the ServerHost parameter, for example: %LeastLoadedHost%.oracle.com.

8.5.2 Changes to Startup Parameters for Oracle Forms Load Balancer Clients

To allow the Oracle Forms Load Balancer Clients to send information about their loads to a highly available Oracle Forms Load Balancer Server, you need to set or change the startup parameters described in the following list. (When you install the Oracle Forms Load Balancer Client, the installation procedure prompts you for the following startup parameters to be used by the Oracle Forms Load Balancer Client.)

  • Data host

    The default value is localhost. In a noncluster environment, this would be the full host name of the system on which the Oracle Forms Load Balancer Server is running. However, for an Oracle Forms Load Balancer Server configured in a cluster, you do not specify a physical node; instead, specify the virtual server address associated with the Oracle Forms Load Balancer Server.

  • Data port

    This must be the same value as is specified for the Oracle Forms Load Balancer Server on every Oracle Forms Load Balancer Client that is associated with the Oracle Forms Load Balancer Server.

8.5.3 Changes to Startup Parameters for Oracle Forms Servers

To allow the Oracle Forms Load Balancer Server to assign workloads to each Oracle Forms Server, adjust the ServerPort parameter in the <Oracle_Home>\FORMS60\Server\formsweb.cfg file to match the Oracle Forms Server port startup parameter.

8.5.4 Changing Startup Parameters for Oracle Forms Load Balancer Server

If you need to change the data port, request port, maximum number of clients, or the trace level for an Oracle Forms Load Balancer Server configured for high availability, do the following:

  1. In the Oracle Fail Safe Manager tree view, select the Oracle Forms Load Balancer Server for which you want to change parameters.

  2. Click the Parameters tab.

  3. Adjust the parameters.

  4. Click Apply.

8.6 Troubleshooting Problems with Oracle Forms Load Balancer Servers

General information about troubleshooting fail-safe resources is in Chapter 6. For general information about troubleshooting Oracle Forms Load Balancer Servers, see the Oracle Forms documentation.

In most cases, the first step in troubleshooting a problem is to issue the Verify Cluster or Verify Group command. These tools are described in general in Chapter 6.

When you issue a Verify Group command on a group containing an Oracle Forms Load Balancer Server, Oracle Fail Safe compares the information in the cluster registry to what is actually written in the configuration files. If the information does not match, Oracle Fail Safe will ask you if you want it to fix the problem.

You can run the Verify Group operation at any time. However, you should run it when any of the following occurs:


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