with replcheck on large tables

We are starting to play with adding this functionality into our production system. We are running 11.50FC8W2 on AIX. When we alter a table to add the witch replcheck we run into a long transaction. We can do this by dropping all our constraints and going to a raw table and be off-line when we do this but that is not the preferred solution. I would rather add this column when we are processing transactions to avoid outage. Suggestions? Am I missing something. Is there not a way that this could be an inplace alter? Thanks in advance. David Link