I need a suppport for this error:
There was an error on the server. Try again or contact site administrators. (Error UID: a2c1fc91-cd7b-43f9-bb58-d6062bcaf7e7)
I use ojdbc7.jar and Oracle 12
You will have to give us more info than that.
Have you loaded the ojdbc7.jar onto the jasperserver ?
When you create a datasource, do you have the option to select the Oracle driver from the drop down list ?
Did you type in the credentials and conneciton details and then when you test the connection it give you the error ?
Also you can you have a look at the jasperserver logs, which will give you much more info that the above message.
You will get a more detailed stack trace error, with more specific reason.