After asking some CakePHP developers I came out with the conclusion that it is not possible to use an Oracle Database with CakePHP 2.3 if you want to make a proper use of CakePHP Models and their query syntax. There's no yet available any driver for Oracle in CakePHP which is completely functional.
Therefore, the solution I found was to use the OCI8 Functions of PHP.
Like this i could use oci_parse
to directly query against the DB or rather call a PL-SQL procedure which is what I finally decided to do. (because of the sql functions complexity and the division of task inside my work group)
Now, I can not make use of many of the advantages of using CakePHP models, but It was the only way.