I need to add a few columns to a multi-master replicated object. This is what I plan to do:

(1) Suspend Master Group
(2) Alter object using dbms_repcat pkg --- Question here
(3) Generate Replication support
(4) Make sure object was modified
(5) Resume Master activity

Questions:
(1) Do I have to suspend the activity at both the Master sites ?
(2) Will the DDL get replicated ?
(3) Can I also add column comments "COMMENT ON COLUMN" in the DDL section ?

Thanks.