+# has to be a full (ie: filled) dump. This might mean one or two
+# extra full dumps are kept until the oldest incremental backups expire.
+#
+# Exponential backup expiry is also supported. This allows you to specify:
+#
+# - num fulls to keep at intervals of 1 * $Conf{FullPeriod}, followed by
+# - num fulls to keep at intervals of 2 * $Conf{FullPeriod},
+# - num fulls to keep at intervals of 4 * $Conf{FullPeriod},
+# - num fulls to keep at intervals of 8 * $Conf{FullPeriod},
+# - num fulls to keep at intervals of 16 * $Conf{FullPeriod},
+#
+# and so on. This works by deleting every other full as each expiry
+# boundary is crossed.
+#
+# Exponential expiry is specified using an array for $Conf{FullKeepCnt}:
+#
+# $Conf{FullKeepCnt} = [4, 2, 3];
+#
+# Entry #n specifies how many fulls to keep at an interval of
+# 2^n * $Conf{FullPeriod} (ie: 1, 2, 4, 8, 16, 32, ...).
+#
+# The example above specifies keeping 4 of the most recent full backups
+# (1 week interval) two full backups at 2 week intervals, and 3 full
+# backups at 4 week intervals, eg:
+#
+# full 0 19 weeks old \
+# full 1 15 weeks old >--- 3 backups at 4 * $Conf{FullPeriod}
+# full 2 11 weeks old /
+# full 3 7 weeks old \____ 2 backups at 2 * $Conf{FullPeriod}
+# full 4 5 weeks old /
+# full 5 3 weeks old \
+# full 6 2 weeks old \___ 4 backups at 1 * $Conf{FullPeriod}
+# full 7 1 week old /
+# full 8 current /
+#
+# On a given week the spacing might be less than shown as each backup
+# ages through each expiry period. For example, one week later, a
+# new full is completed and the oldest is deleted, giving:
+#
+# full 0 16 weeks old \
+# full 1 12 weeks old >--- 3 backups at 4 * $Conf{FullPeriod}
+# full 2 8 weeks old /
+# full 3 6 weeks old \____ 2 backups at 2 * $Conf{FullPeriod}
+# full 4 4 weeks old /
+# full 5 3 weeks old \
+# full 6 2 weeks old \___ 4 backups at 1 * $Conf{FullPeriod}
+# full 7 1 week old /
+# full 8 current /
+#
+# You can specify 0 as a count (except in the first entry), and the
+# array can be as long as you wish. For example:
+#
+# $Conf{FullKeepCnt} = [4, 0, 4, 0, 0, 2];
+#
+# This will keep 10 full dumps, 4 most recent at 1 * $Conf{FullPeriod},
+# followed by 4 at an interval of 4 * $Conf{FullPeriod} (approx 1 month
+# apart), and then 2 at an interval of 32 * $Conf{FullPeriod} (approx
+# 7-8 months apart).
+#
+# Note that you will have to increase $Conf{FullAgeMax} if you want
+# very old full backups to be kept. Full backups are removed according
+# to both $Conf{FullKeepCnt} and $Conf{FullAgeMax}.
+#
+# Note also that these two settings are equivalent and both keep just
+# the four most recent full dumps:
+#
+# $Conf{FullKeepCnt} = 4;
+# $Conf{FullKeepCnt} = [4];