ZF2's documentation on connecting to an Oracle db is sparse at best. Here are a couple of examples of how to setup the connection. This is a basic connection. Note the character_set key. If this isn't set the Oracle driver will improperly encode special characters when sending and receiving data.
'db' => array(
'driver' => 'Oci8',
'connection' => 'orcl', // Name of conenction in tnsnames.ora
'username' => 'username', // Username to access db
'password' => 'password', // Password to access db
* Explictly set the character set here or the oracle driver will create null characters where
* special characters are used.
'character_set' => 'AL32UTF8',
Here is an example of setting up multiple Oracle connections.