[p4] Backup and restore

[Paul Goffin]

>However, it is worth bearing in mind that checkpoint.3 = checkpoint.2 +
journal.2

Actually, that's not exactly true.  Checkpoint.3 is what you'd get if you
checkpointed the meatdatabase formed by checkpoint.2 + journal.2

The journal.2 file may contain records of additions, obliterations and
modifications to change specifications, etc. that would ultimately not be in
the checkpoint.3

>So the journals are an audit trail of what happened between the checkpoints
(which can on occasion be useful to work out some sequence of events). Thus
keeping journals for some period of time can be worth it.

Journals are a complete audit trail.  A record of successive checkpoints
isn't.

Paul.