Yes, you are right... The references to "DB2 mode" is from the past, leftover comments. There is no distinction between the two.

Satheesh

Bernt M. Johnsen wrote:
Hi all!

In the Derby source, I find several comments referring to "DB2 mode"
and "Cloudscape mode". I can't, however, find any code related to a
distinction between these two modes. Are these comments "leftovers"
from the pre-Derby period of the code, or have I missed something?

The reason I wonder is the error message

ij> create table tab (i integer primary key);
ERROR 42831: 'I' cannot be a column of a primary key or unique key because it can contain null values.

and comments in the code like

  
* Set all columns in that appear in a primary/unique key constraint in a create
* table statement to NOT NULL in Cloudscape mode and raises an error in DB2 mode.
    

and 

  
 /* For primary/unique/unique keys, verify that the constraint's column
  * list contains valid columns and does not contain any duplicates
  * (Also, all columns in a primary key will be set to non-null,
	but only in Cloudscape mode. SQL and DB2 require explict NOT NULL.