org.hibernate.dialect.DB2390Driver.supportsSequences() returns "false".
So it is not possible to use id generator strategy "enhanced-sequences" with this db2 driver configuration.
But this behaviour is not correct, at least DB2 V11 for z/OS supports sequences.
So DB2390Driver.supportsSequences() should return "true" (or should be removed). In this case, it should work fine, because correct sequence handling seems to be implemented in superclass DB2Driver.
Hibernate 5.2.x (and previous) with DB2 V11 OS 390