Setting an Oracle Environment variable – ORACLE_HOME

Hello,When I check my blog hit counter statistics, my blog is being hit and searched by the blog users with the word “Oracle Home”, but, looks like they are not finding the required information on “Oracle Home” Environment variable. So, I wanted to explain about ORACLE_HOME in my simple terms which is helpful for novice.What is ORACLE_HOME used for?* The ORACLE_HOME is an environment variable which is used to set and define the path of Oracle Home (server) Directory.* The ORACLE_HOME directory will have the sub directories, binaries, executables, programs, scripts, etc. for the Oracle Database.* This directory can be used by any user who wants to use the particular database.* If the ORACLE_HOME variable is defined as an environment variable, then during the installation process, the Oracle Home Path will be set to the directory defined as default. If the variable is not defined, then the Oracle will take its own default location. i.e. The ORACLE_HOME variable does not have to be preset as an environment variable, it can be set during the installation process.* Basically The ORACLE_HOME variable is in the following ORACLE_BASE directory:ORACLE_HOME=$ORACLE_BASE/product/10.2.0.What is ORACLE_BASE used for?* The ORACLE_BASE is also an environment variable to define the base/root level directory where you will have the Oracle Database directory tree - ORACLE_HOME defined under the ORACLE_BASE directory.* Basically, The ORACLE_BASE directory is a higher-level directory, than ORACLE_HOME, that you can use to install the various Oracle Software Products and the same Oracle base directory can be used for more than one installation.Note: If you did not set the ORACLE_BASE environment variable before starting OUI, the Oracle home directory is created in an app/username/directory on the first existing and writable directory from /u01 through /u09 for UNIX and Linux systems, or on the disk drive with the most available space for Windows systems. If /u01 through /u09 does not exist on the UNIX or Linux system, then the default location is user_home_directory/app/username.How to check if ORACLE_HOME is set already?On Unix/Linux Systems:Basically, before or after the Oracle Database is installed, the oracle user profile, the environment variable file, is prepared where all the required environment variables for Oracle are set. i.e. ORACLE_BASE, ORACLE_HOME, ORACLE_SID,PATH, LD_LIBRARY_PATH, NLS_LANG, etc.The user profile file can be.bash_profile – Bash Shell.profile – Bourne Shell or Korn shell.login­ – C ShellNote: This user profile file will be under user’s home directory i.e. $HOME/.bash_profileTo check specific environment variable set:$ echo $ORACLE_HOMETo check all the environment variables set:$ envOn Windows Systems:To check specific environment variable set:C:\> set ORACLE_HOMEORC:\echo %ORACLE_HOME%To check all the environment variables set:C:\> setOrC:\> envOther way, to check the ORACLE_HOME, is as follows.Start -> Run -> Regedit (enter) -> HKEY_LOCAL_MACHINE -> SOFTWARE –> ORACLEi.e. My Computer\HKEY_LOCAL_MACHINE\SOFTWARE\ORACLEHow to check using sqlplus command:To find the ORACLE_HOME path in Oracle DatabaseHow to set the ORACLE_HOME environment variable?On Unix/Linux Systems:Define the ORACLE_HOME value in the user profile file i.e. .bash_profile or .profileORACLE_HOME=$ORACLE_BASE/product/10.2.0export ORACLE_HOMESource the user profile as follows:Bash shell:$ . ./.bash_profileBourne shell or Korn shell:$ . ./.profileC shell:% source ./.loginIf no profile file is set with environment variables, then physically also be set as follows:Bourne, Bash, or Korn shell:$ ORACLE_BASE=/oracle/app$ export ORACLE_BASE$ ORACLE_HOME=$ORACLE_BASE/product/10.2.0$ export ORACLE_HOMEC Shell:% setenv ORACLE_BASE /oracle/app% setenv ORACLE_HOME /oracle/app/product/10.2.0On Windows Systems:My Computer -> Properties -> Advanced -> Environment Variables -> System Variables -> New/Edit/Delete (to set the variables)After setting the environment variables as above, open a fresh CMD tool and check whether they set properly or not. Do not try on already opened CMD tool to make sure the variables set or not.Another way to physically set the variables as follow at the DOS prompt:C:\> set ORACLE_HOME=C:\oracle\app\product\10.2.0C:\> echo %ORACLE_HOME%Note: I would suggest to refer the Oracle Documentation on Installation where these environment variables are discussed and explained with the enough information.

Regards:
Shahid ul Ghani
http://www.dbashahid.blogspot.com