Also, as a safety hook for users migrating I added a setting to opt back into the legacy mapping : hibernate.dialect.oracle.prefer_longvarbinary (org.hibernate.dialect.Oracle12cDialect#PREFER_LONGVARBINARY). It defaults to false meaning that by default, starting in 5.1 Oracle12cDialect will map byte[] and Byte[] to BLOB rather than LONG (LONGVARBINARY).