Tools available in Oracle to locate the 'Oracle Home' Directory

As an Oracle Database Administrator (DBA) working with Oracle Shared Server, determining the location of the 'Oracle Home' directory is a crucial task. Oracle Home is a directory path in which the Oracle Database’s executables and libraries reside. For Oracle 19c, there are multiple methods to ascertain the Oracle Home directory.

1. Environment Variables: Oracle Home can be found using environment variables. On UNIX or Linux systems, you can execute the command
   

   `echo $ORACLE_HOME`
   

   
   in the terminal. On Windows systems, you may use the command
   

   `echo %ORACLE_HOME%` 
   

   
   in the Command Prompt. It is imperative to note that this method is contingent on the environment variable being correctly set.
2. Oracle Inventory: The Oracle Inventory directory contains information pertaining to all Oracle software installed on the system. You can locate the Oracle Home directory by examining the `inventory.xml` file located in the Oracle Inventory directory. The path to this directory is often
   

   `/etc/oraInst.loc` 
   

   on UNIX or Linux, or `C:\Program Files\Oracle\Inventory` on Windows.
3. Database Query: If you have access to the Oracle Database, executing a query can yield the Oracle Home directory. You can run the following SQL query using a tool like SQL*Plus or SQLcl:
   

   SELECT SYS_CONTEXT('USERENV', 'ORACLE_HOME') FROM DUAL;
   

   
   This command will return the Oracle Home directory for the current session.
4. Oracle Configuration Files: Certain Oracle configuration files, such as `tnsnames.ora` or `listener.ora`, can be located in the `$ORACLE_HOME/network/admin` directory. If you know the path to these files, you can backtrack to find the Oracle Home directory.
5. Oracle Universal Installer (OUI): The Oracle Universal Installer maintains records of all Oracle software installations. You can use the OUI to view the Oracle Home details. On UNIX or Linux, navigate to the Oracle Inventory directory and execute the `opatch lsinventory` command.
6. Oracle Home Selector: For systems with multiple Oracle Home directories, the Oracle Home Selector tool can be employed to view and select the active Oracle Home. This tool is typically used on UNIX and Linux systems.
7. Operating System Commands: On UNIX or Linux systems, commands such as `find` or `locate` can be utilized to search for specific Oracle executables or libraries, thus leading you to the Oracle Home directory. For instance, you could use a command like `find / -name sqlplus` to search for the `sqlplus` executable.
8. Check Oracle Documentation: Oracle’s official documentation often provides detailed instructions and scripts for locating the Oracle Home directory. Ensure that you are referring to the documentation pertinent to Oracle 19c and your specific operating system.

Ascertaining the location of the Oracle Home directory in Oracle 19c is a multifaceted task, with various tools and methods at your disposal. The method chosen should be based on your specific environment and the level of access you possess. It is crucial to proceed with caution, particularly when executing commands or queries, to ensure the security and integrity of your Oracle Database environment.

Next we are going to discuss the Oracle Home directory. When you install Oracle software, you end up with a large directory structure that contains all the executables and other files that make Oracle work. All these directories sit under one top-level directory referred to as the Oracle Home directory. The diagram below shows some of the directories that you might find in a typical installation. Move your mouse over the diagram to learn about each directory:

If you are running the UNIX operating system, you will have an environment variable named ORACLE_HOME that points to the top-level Oracle directory. You can make that directory your current working directory by issuing the following command:

cd $ORACLE_HOME

The Unix environment variable `$ORACLE_HOME` still exists in the Oracle 19c release of the RDBMS. It is used to specify the location of the Oracle installation directory. This variable is used by many Oracle tools and utilities, such as SQL*Plus, to find the necessary libraries and executable files.
To set the `$ORACLE_HOME` environment variable, you can use the following command:

export ORACLE_HOME=/path/to/oracle/installation/directory

For example, if you installed Oracle 19c in the directory

	
`/u01/app/oracle/product/19c`

, you would set the `$ORACLE_HOME` environment variable as follows:

export ORACLE_HOME=/u01/app/oracle/product/19c

Once you have set the `$ORACLE_HOME` environment variable, you can start using Oracle tools and utilities. For example, to start SQL*Plus, you would run the following command:

sqlplus

SQL*Plus will use the `$ORACLE_HOME` environment variable to find the necessary libraries and executable files. If you do not set the `$ORACLE_HOME` environment variable, you may receive an error message when trying to use Oracle tools and utilities.

By default, when you start Oracle Universal Installer, the software searches your system to determine the default Oracle home where Oracle software should be installed. In all cases, the ORACLE_HOME name is taken first from the command line if it is specified, or else from the response file if specified.
If not specified, the value of DEFAULT_ORACLE_HOME_NAME in the oraparam.ini file is examined.

The Oracle Universal Installer (OUI) is still used for Oracle 19c. It is the primary installation tool for all Oracle products, including the database, Grid Infrastructure, and other Oracle software. The OUI is a graphical user interface (GUI) installer that guides users through the installation process step-by-step. It allows users to select the components they want to install, specify the installation location, and configure the software.
The OUI is a powerful and flexible installation tool, but it can be complex to use. Oracle also provides a command-line installer (CLI) for users who prefer to install Oracle software using the command line.
Here are some of the benefits of using the OUI to install Oracle 19c:

1. It is a GUI installer, which makes it easy to use, even for users who are not familiar with the command line.
2. It is a flexible installer, allowing users to select the components they want to install and specify the installation location.
3. It is a powerful installer, providing a variety of features, such as the ability to configure the software and perform prerequisite checks.

If you are new to Oracle, I recommend using the OUI to install Oracle 19c. It is the easiest and most straightforward way to install the software.