Oracle 12c client has a known memory leak as per Oracle Support. Memory leak is between 110-120k per Oracle client session (connection) when using the oracle probe.
1. Install Oracle client 220.127.116.11 (11g libraries are installed as part of the client install.) The 12c libs were still in place.
2. The Robot environment had to be configured for the 11g client.
variable name variable value
3. Cold start the oracle probe (Deactivate-Activate)
The memory leak issue should be averted.