What is ORATAB

• What is ORATAB and what is it used for?

  "oratab" is a file created by Oracle in the /etc or /var/opt/oracle directory when installing database software. This file may contain comments staring with a pound signs (#) in column one, and data lines consisting of entries in the following format:
  
  database_sid:oracle_home_dir:Y|N
  
  - database_sid is the system id (SID) of an Oracle instances on the server.
  - Oracle_home_dir is the ORACLE_HOME directory associated with this instance.
  - The Y|N flags indicate if the instance should automatically start at boot time (Y=yes, N=no).
  
  Besides acting as a registry for what databases and software versions are installed on the server, ORATAB is also used for the following purposes:
  
  
• Oracle's "dbstart" and "dbshut" scripts use this file to figure out which instances are to be start up or shut down (using the third field, Y or N).
• The "oraenv" utility uses ORATAB to set the correct environment variables.
• One can also write Unix shell scripts that cycle through multiple instances using the information in the oratab file.

 

Open file ‘oratab‘ using vi editor and make changes shown below:

# vim /etc/oratab orcl:/u01/app/oracle/product/12.1.0/db_1:Y