NEWBIE: How much "disconnected data" it too much?

Dear Experts,

I'm a C# newbie (via Java) looking at ADO.NET for the first time.

I'm trying to understand when you would use "disconnected data", using DataSets and DataAdapters.  My understanding so far is that although the "disconnected data" behaves as though it were a little mini-database, it's all actually being stored IN MEMORY.  Is that right?

If so, it seems there must be some vague upper limit.  For instance, my Java application might currently retrieve 100,000 customer records, each of say 500 bytes (=50Meg), using a traditional "connected" ResultSet.  Is it practical to hold all that in a "disconnected" DataSet?

Thanks!
BrianMc1958