Oracle initialization file existence is a “mandatory” pre-requisite before starting up the database, otherwise you won’t be able to startup the database.

The initialization file is a configuration file used for example to adjust memory parameters and control file locations.

There are 2 types of initialization files:

• Server parameter file (spfile)
• Init.ora text file

The first type (spfile) can be used if you require to change the contents of the file using sql statement (ALTER SYSTEM) command. Also, if you use spfile you can remotely start the database from your client machine.

The second type (init.ora) text file can be edited using OS text editor, and you can add hash comments while performing modifications. I personally prefer using this type of initialization file.

The location of initialization of file is under $ORACLE_HOME/dbs  directory

The init file would like the following:

spfile<SID>.ora       OR    spfile.ora     OR    int<SID>.ora

Where <SID> is the oracle database instance system id

Recommendation:

In 11g and 12c set the memory_target and memory_max_target initialization parameters, this setting will enable automatic memory management.