<p>The source database is quite large. The target database doesn't grow automatically. They are on different machines.</p>

<p>I'm coming from a MS SQL Server, MySQL background and IDS11 seems overly complex (I am sure, with good reason).</p>

have you used the export tool ?  There used to be a way if you first put the db's into quiescent mode and then you could actually copy the DBSpaces across (dbspaces tool I think... its been a few years now).
Because with informix you used to be able to specify the DBSpaces(s) to used for the table (maybe even in the alter table ?).
Check - dbaccess tool - there is an export command.
Put the DB's into quiesent mode or shut down, copy the dbspaces and then attach table telling it to point to the new dbspaces file.  (the dbspaces tool could be worth while looking at.. I have manuals around here.  they are 9.2, but it shouldn't have changed too much).