@OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL, mappedBy = "DO1")
private Set<DO2> do2Set;

@JsonBackReference("name")
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "key", referencedColumnName = "key")
private DO1 do1;

@SequenceGenerator(name="SEQ",sequenceName="QTY_SEQ", allocationSize = 500)

"org.hibernate.exception.ConstraintViolationException: could not execute statement", "embeddedExceptions": [{"message": "org.hibernate.exception.ConstraintViolationException: could not execute statement" }]}"

Error Msg = ORA-00001: unique constraint () violatednntat oracle.jdbc.driver.T4CTTIoer11.processError(T4CTTIoer11.java:498)nt... 50 moren