The update files are sorted before being processed because there are
cases where order matters (such as getting schema added first, creating
parent entries, etc).

Updates are applied in blocks of ten so that any entries that are dependant
on another can be added successfully without having to rely on the length
of the DN to get the sorting correct.

The file names should use the format #-<description>.update where # conforms
to this:

10 - 19: Configuration
20 - 29: 389-ds configuration, new indices
30 - 39: Structual elements of the DIT
40 - 49: Pre-loaded data
50 - 59: Cleanup existing data
60 - 69: AD Trust
70 - 79: Reserved
80 - 89: Reserved

These numbers aren't absolute, there may be reasons to put an update
into one place or another, but by adhereing to the scheme it will be
easier to find existing updates and know where to put new ones.
