Before installing the new Oracle EBS 12i release, these are the disk space requirements

Rapid Install installs the file system and database files for all products, regardless of
their licensed status. The approximate file system requirements in a standard
installation are:

Applications node file system (includes AS
10.1.2 ORACLE_HOME, AS 10.1.3
ORACLE_HOME, COMMON_TOP,
APPL_TOP, and INST_TOP)
28 GB
Database node file system (Fresh install) 45 GB
Database node file system (Vision Demo database)
133 GB
The total space required for a standard system,
not including the stage area, is 73 GB for a fresh install with
a production database, and 161 GB for a fresh install with a Vision
Demo database.

Note: The database node disk space requirements for both the
production database and the Vision Demo database include database
1-10 Oracle Applications Installation Guide: Using Rapid Install
files (.dbf) and the 10g R2 database ORACLE_HOME.
Stage area

For a production database install, running Rapid Install from a stage area requires at
least 33 GB to accommodate the file system and database files in the stage area.