> What are these files and why have they suddenly started to be created
> and why so large?
They're the contents of the database and they get created every time there
is another 1GB worth of data in there. Note that the database will use
more space if data is being UPDATEd and you don't vacuum it regularly.
Without the vacuum going it's as if you'd added a new row instead when you
While it's possible to decode what those files are by using oid2name or
pg_class, what you probably want to know instead is what the big tables
and indexes in your database are to figure out what is gobbling space.
The script at http://wiki.postgresql.org/wiki/Disk_Usage will give you