You are running URT on Enforce server on 14.6 before upgrade to 15.5 and you are getting errors.
Errors on URT:
ORA-03114: not connected to ORACLE
ERROR at line 6:
ORA-06550: line 6, column 7:
PLS-00201: identifier 'UPGRADESCHEMA_V15_5_0.MAIN_DRIVER' must be declared
Errors on Database:
PGA memory used by the instance exceeds PGA_AGGREGATE_LIMIT of 4096 MB
Adjust memory value on Database. This should be completred by customer's database team as darabase with RAC is not supported yet.