Locking Down a Database

Greetings:

I occasionally find the need to perform some maintenance on one or more of
thirteen different databases. Typically, due to the interaction between the
databases, I need to lock down the databases for a short period of time so
that no updates are being performed anywhere. I do not want to shut down the
postmasters as it is a clustered environment and would rather just leave that
alone. Also, since this is a 24 hour shop, it would be good if people could
still query, but not change any data. All this work is done at times like
03:00 in the morning and the number of people working at that time is limited
to five or six. Is there some easy way of doing this without having people log
out of the application?

TIA...
--
Terry Lee Tucker
tel: (336) 372-5432; cell: (336) 404-6897
terry(at)chosen-ones(dot)org