You opened a lot of connections and that’s the issue. I think in your code, you did not close the opened connection.
A database bounce could temporarily solve, but will re-appear when you do consecutive execution.
Also, it should be verified the number of concurrent connections to the database. If maximum DB processes parameter has been reached this is a common symptom.
Courtesy of this thread: https://community.oracle.com/thread/362226?tstart=-1