On-line backup and point-in-time recovery (PITR)

Hi All,

I have a couple of questions regarding On-line backup and point-in-time
recovery (PITR) in the postgres documentation:

1.How is it that we can create a tar file of the PG Data directory
whilst postgres is running?

2.What happens with any DB inserts, updates, deletes etc that occur
between the SELECT pg_start_backup() and the end of the tar?
They would be already logged in the WAL files and already applied in the
tarball, do they then get duplicated during log replay in the recover
process?

Thanks In Advance

Enzo D'Addario...

pieNETWORK's Ltd...