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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. It is used to list the databases and software versions installed on a server.

 

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.

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Oracle Database Architecture

 

 

How to check log files location: You can see the log file locations by running the following command.

$sqlplus / as sysdba

SYS@test SQL>show parameter dump_dest

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
background_dump_dest            string      /u01/app/oracle/admin/test/bdump
core_dump_dest                       string      /u01/app/oracle/admin/test/cdump
user_dump_dest                       string      /u01/app/oracle/admin/test/udump                                  

Basic Tips 1:

When Oracle is trying to open your database, it goes through three distinct stages These stages are:

* Startup (nomount)

* Mount

* Open