Need information on Oracle Snapshots

Can anybody out there point me in the direction of any documentation (on-line or paper based) that describes Oracle's Snapshot facilities in greater detail than the Oracle manuals?
The information I'm after can be summarised as follows: 1. What system tables are used to keep track of the snapshots?

   (Through experimentation I've sussed out SNAP$, SLOG$ & MLOG$     are there any others?)
2. How does Oracle keep track of multiple 'snapshots' of the same table(s)? 3. Given a simple snapshot and a snapshot log at the source site, what

   conditions will cause Oracle to return a 'FAST REFRESH cannot be used'    error when trying to do a fast refresh?    (We've had lots of problems with this one and I'm particularly interested     in understanding the mechanisms behind fast refreshes.)

My database is in the UK with 44 simple snapshots of tables in a US based database (time difference = 5 hours).
Any assistance will be much appreciated, Michael.

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