Recently, faced an issue in one of our oracle databases running on 12.1, that the listener was spawning a child process every few minutes. Also, we could observe high listener latency of ~5000ms.
At first, stopped the listener and started it again, but it did not help at all.
Then, checked the listener log and saw connection coming to the order of 100times the normal connections. Got the application bounced. It helped temporarily and after sometime, got the same problem back.
Finally we got the root cause -the sqlnet.ora was somehow renamed to sqlnet.or and this was causing connections. Once the file was renamed to sqlnet.ora, everything went fine
