Maintainence of universe means adding new tables, 
refreshing the table structure after adding new tables,
create the joins between the new tables to existing tables,
identify loops if any, examine the integrity checks after 
any changes, determining the cardinality if any,resolving 
the loops, adding the new objects and classes , exporting , 
restricting access to users,etc..

all the operations after the initial production phase are 
maintainence

mean that we have to add some more tables to scheema design 
as per client requirements.and fine any prob if u add the 
tables.resolve and generate reports