>One question, about how many tables are we talking about, and how many rows in the big tables? Also, are you doing any partitioning?

234 tables
5 millions to 20 millions on the big tables
No partitioning

>On the 24x7, who deemed that, the client? Reason I ask, unless we are talking about a mission critical database (say, medical transactions or stock transactions), I think 24x7 is sometimes a pipe dream. Even Wells Fargo (my bank) has a brief period overnight where they are down.

We need to work on that. I'll see what can be done to have a better window of such maintenance.