Hi @francisco.fernandes and welcome to the checkmk forum. 
I’m pretty sure you can fix your issue by updating your checkmk server to a supported and newer version. The version you are using is quite old and not supported anymore.
In the meantime a lot of changes have been made to the mk_oracle check plugin as you can see in the werks.
Please update your site according to the official documentation from 2.0.0 to 2.1.0 and then 2.2.0.
Hope this helps. 
Regards
Norm