Online backups and tar

1. Section 23.3.2 (Making a Base backup) of the 8.1.0 doc says:

"Also, some versions of GNU tar consider it an error if a file is changed
while tar is copying it. There does not seem to be any very convenient way
to distinguish this error from other types of errors, other than manual
inspection of tar¹s messages. GNU tar is therefore not the best tool for
making base backups."

What then, on linux (Red Hat 3.0 ES), is the recommended backup program for
online backups? It appears cpio does the same thing.

2. During a restore, postmaster tries to restore a file '00000001.history'.
Neither that file, nor any *.history file, is anywhere to be found. I can
not find this documented anywhere. What is this file? Does it have to do
with timelines?

Wes