Please Set Event 10055 in Oracle Database 12c to Avoid Possibly Wrong Results
Please see this important announcement, concerning possibly wrong results. Oracle Support is recommending that you set the following event in your server parameter file as a workaround.
event = "10055 trace name context forever, level 2097152"
The root cause is Bug 22173980.
Alternatively, if you find Patch 22173980 available on My Oracle Support for your release level and platform, then please download and apply it. (Please apply this patch to a test system before using in production. Please consult the README file accompanying this patch.) If you do not find it, and if your release level still qualifies for patching, then you may open a service request, so that the patch may be constructed for your particular release level and platform.