[Installing Oracle DataBase Server 11.2.0.3 on Oracle Linux 6.3]: Configuring Oracle Autostart After Reboot

$ vi /etc/oratab

ora112:/u01/oracle/database/11.2:N

replace with

# ora112:/u01/oracle/database/11.2:N
ora112:/u01/oracle/database/11.2:Y

Creating a script to start and stop the database at system startup and shutdown:

Create a database startup script with the following content.

# vi /etc/rc.d/init.d/startupOracleDatabase11GR2

content:

https://bitbucket.org/oracle-dba/oracle-dba-startup-and-shutdown-scripts/raw/b6be770160490abcc906953237985ddcfa2c7224/oracle_11GR2_startup_and_shutdown_script

# chmod +x /etc/rc.d/init.d/startupOracleDatabase11GR2
# chkconfig --add startupOracleDatabase11GR2
# chkconfig --level 345 startupOracleDatabase11GR2 on

I recommend going directly to the latest version of the document, which uses newer software versions

Link to the Oracle installation document.