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Oracle Universal Installer Concepts Guide
Release 2.2

Part Number A96697-01
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Using Multiple Oracle Homes


The Oracle Universal Installer supports the installation of several active Oracle homes on the same machine. An Oracle home is the system context in which Oracle products run. This context consists of the directory location where the products are installed, the corresponding system path setup, and where applicable, the program groups associated with the products installed in that home, and the services running from that home.

Multiple Oracle Homes

The Oracle Universal Installer supports the installation of several active Oracle homes on the same machine as long as the products support this at runtime. You can have multiple versions of the same product or different products running from different Oracle homes concurrently. Products installed in one home will not conflict or interact with products installed in another home. You can update software in any home at any time, assuming all Oracle applications/services/processes installed on the target home are shut down. Processes from other homes may still be running.

Target Home

The Oracle home currently accessed by the Oracle Universal Installer for installation or deinstallation is the target home. In order to upgrade or remove products from the target homes, those products must be shut down/stopped.

Product Types

Different levels of support are available with multiple Oracle homes for the following product types:

Home Selector (Available on Win32 Platforms)

The following sections describe the Home Selector application, which is available when you install the Oracle Universal Installer on a Windows computer.


The Home Selector is part of the installation software and is installed with the Oracle Universal Installer. It is installed in <oui_location>\HomeSelector.

If your application is not installed in one of the Oracle homes, you need to ensure it uses the right product version, by pointing it to the right home. That specific (target) home must take precedence over the other homes in your path when you launch your application.

The Home Selector enables you to easily change your primary Oracle home (the one that appears first in the PATH environment variable). If you need to switch the active home or need to perform batch work which requires a "default home" to be active, the Oracle Home Selector can be used to change the Windows NT system settings.

When using the Home Selector to make a specific $ORACLE_HOME the active one, the software installation in question is moved to the top of the PATH variable, making it the first directory to be scanned for executables and library files.

How It Works

When you perform an install on a system, the first $ORACLE_HOME will be named the "DEFAULT_HOME" and will register itself in the Windows NT registry under the key:


This is the default Windows NT registry hive which contains all the "generic" Oracle settings. Also the PATH variable is adjusted and the BIN directory of the $ORACLE_HOME is added to the environment variable.

Starting with Oracle 8.0.4, the first version to be multiple $ORACLE_HOME aware, some additional parameters will also be written to the key:


With the Oracle Universal Installer, you can change the "DEFAULT_HOME" name to something else. Also, it registers all Oracle settings in the "Home0" subkey of the ORACLE key.

When an additional $ORACLE_HOME is added to the system, the PATH variable is adjusted again to add the new BIN directory of the newly installed Oracle software. The registry variables are written to a key named "HOMEx," where X is the next available number in the Oracle key.

When several $ORACLE_HOMEs are installed, the executables referenced are all found in the first $ORACLE_HOME\BIN directory of the PATH variable. When you want to switch the order of the PATH variable, you can use the Home Selector to switch the order of the $ORACLE_HOMEs installed on the system.

Together with the installation and registration of the software in the registry, a second series of registry variables are written in the following key:


This is the starting point for the list of all $ORACLE_HOME installations, done on this system.

The following variables are written in this key:

If the Home Selector is started in interactive mode, the registry hive "ALL_HOMES" is read, including all subkeys, and a dialog box will be displayed with all available installations. As soon as the you select one, the PATH variable will be adjusted at the system level.

In order to make batch processing possible, this tool also has a command line interface, making it possible to use the tool to switch the PATH settings while executing a series of commands:

ohsel -switch "Oracle Home Name"

The name of this $ORACLE_HOME is one of the names found in the ID subkeys.

Oracle Home Directory Structure for Windows Platform

A typical Oracle home on Windows platforms contains the files and directories shown in Table 2-1.

Table 2-1 Oracle Home Directory for Windows Platforms
Oracle Home Directory Contents


Product executables and DLLs


Common message files


PROD1 product files


PROD2 product files

Optimal Flexible Architecture Directory Structure (on Solaris)

The Optimal Flexible Architecture (OFA) standard is a set of configuration guidelines for fast, reliable Oracle databases that require little maintenance.

OFA is designed to:

The OFA directory structure is described below.


ORACLE_BASE specifies the BASE of the Oracle directory structure for OFA-compliant databases. A typical ORACLE_BASE directory structure is described in Table 2-2. When installing an OFA-compliant database using the Oracle Installer, ORACLE_BASE is by default set to /pm/app/oracle.

Table 2-2 Sample ORACLE_BASE Directory Structure and Content
Directory Content


Administrative files


online documentation


Subtree for local Oracle software


Oracle software


The following is an example of an Oracle Server Install.

If you install an OFA-compliant Oracle Server, the ORACLE_HOME directory is /mount_point/app/oracle/product/release_number. ORACLE_HOME directory structure and content are described in Table 2-3. Under UNIX, the ORACLE_HOME directory might contain the following subdirectories, as well as a subdirectory for each Oracle product selected.


The examples in this table are for sample only. The directories that appear in your own Oracle Home will depend upon whether the corresponding products are installed and the version of the Oracle database you are running.

Table 2-3 Sample ORACLE_HOME Directory Structure and Content
Directory Content


configuration Assistants


binaries for all products


interMedia Text cartridge


initsid.ora, lksid


install related files


Oracle product libraries


Java classes


Spatial cartridge


Xerox Stemmer (for interMedia Text cartridge)




NLS runtime loadable data


common files for all products


data gatherer


Parallel Server Manager Components


core libraries


data cartridges


Oracle TRACE






server files and libraries required for the database


SLAX parser



Creating an Oracle Home

To create an Oracle home, follow the steps below.

  1. Run the Oracle Universal Installer.
  2. In the File Locations page, enter the Oracle home settings for the installation session under Destination. See Table 2-4 for a description of the fields in this section of the screen.


    The Name field only appears in Windows platforms.

  3. Continue with your installation. Refer to Chapter 1, "Using the Oracle Universal Installer" for detailed information.
    Table 2-4 Oracle Installation Settings in Destination  
    Settings Functions


    For Windows platforms, Oracle homes are identified by name, and the Oracle home name identifies the program group associated with a particular Oracle home, and the Oracle services installed on the associated home. The Oracle home name must be 1 to 16 characters long and can only include alphanumeric characters and underscores.


    Enter an Oracle home and its full path or select an Oracle home from a drop down list of existing Oracle Homes. The Oracle home location is the directory where products are installed.

    List of Oracle homes on Windows platforms:

    • All Oracle homes that are already created using the Oracle Universal Installer
    • All homes created using the previous Oracle Installer (ORCA-based)
    • The home that the ORACLE_HOME environment variable points to

    List of Oracle homes on UNIX:

    • All Oracle homes that are already created using the Oracle Universal Installer
    • All homes as defined in the /var/opt/oratab file
    • The home that the ORACLE_HOME environment variable points to

    If none of these homes exists, a default home is calculated based on the disk volume with the largest amount of free space.

    Datafiles may or may not be installed within an Oracle home. You may use the Browse button to choose a directory to install your product.

    For Windows platforms: it must be a valid path that is not in the Windows directory. Different homes cannot share the same location.

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