TIBCO have confirmed the iProcess(R) Engine versions 11.6.1 and 11.7.0 have not been specifically been tested/certified with Oracle 19c. However based on compatibility this combination should work and is supported by TIBCO.

For iProcess Engine 11.6.1 the Oracle Client must be 12.1.0.2
For iProcess Engine 11.7.0 the Oracle Client must be 12.2.0.1

Therefore depending on the version of iProcess(R) Engine being used the appropriate version of Oracle Client must be used to connect to the Oracle 19c database.