Currently DB2Dialect uses ", " for cross joins because 9.1 does not support "cross join" syntax. DB2 has problems combining ", " with "join" syntax, so the fix for does not work on DB2.
Although DB2 9.1 reached its end of life April 30, 2015, some applications may still be using that version, so I will create a new DB2 dialect that extends DB2Dialect and overrides getCrossJoinSeparator() to return " cross join ".
The question is what to call the new dialect.
According to DB2 9.5 and 9.7 documentation, "cross join" syntax is supported in those versions. I am able to confirm this on 9.7, but I do not have access to DB2 9.5 to try it out.
If someone can confirm this will work on DB2 9.5 by the time Hibernate 5.2.9 is released, then I'll name the new dialect DB295Dialect; otherwise, I'll name it DB297Dialect.