Resolving SP2-0750: You may need to set ORACLE_HOME to your Oracle software directory

If you set up Oracle Database XE 11G in Linux and you encounter the following error when starting up SQL Plus:

$ sqlplus
SP2-0667: Message file sp1<lang>.msb not found
SP2-0750: You may need to set ORACLE_HOME to your Oracle software directory

To resolve it try the following. It's assumed Oracle XE 11G is installed at:

/u01/app/oracle/product/11.2.0/xe/

If you have a different set up, adjust your directory path accordingly.

1) Find out the path to sqlplus
    bash-3.2$ which sqlplus
   /u01/app/oracle/product/11.2.0/xe/bin/sqlplus

2) Set your Oracle_HOME (upto xe directory)

   bash-3.2$ export ORACLE_HOME=/u01/app/oracle/product/11.2.0/xe/

3) Set the path to the directory where sqlplus is located to your PATH variable:

    bash-3.2$ export PATH=/u01/app/oracle/product/11.2.0/xe/bin:$PATH

 
You should now be able to use sqlplus. 

4) Now you need to edit you bash_profile so all these takes effect everytime you log in.

bash-3.2$ cd ~/
bash-3.2$ vim .bash_profile

5) In the .bash_profile you will need to add those export lines so every time you log in the same settings take effect.

bash-3.2$ vim .bash_profile
# .bash_profile

# Get the aliases and functions
if [ -f ~/.bashrc ]; then
        . ~/.bashrc
fi

# User specific environment and startup programs
ORACLE_SID=XE
export ORACLE_SID
ORACLE_HOME=/u01/app/oracle/product/11.2.0/xe
export ORACLE_HOME
PATH=$ORACLE_HOME/bin:$PATH
export PATH
unset USERNAME


6) Run the following:
bash-3.2$ . .bash_profile
 
After following these 6 steps you should be able to connect to sqlplus any time.