There are SQL sequences that should not neccessarily be performed every time you
update your database structure. Rather, these queries should be executed once or
from time to time. Essentially, an .sql file should appear under 'maintenance'
instead of the old 'updates' folder provided that:

- Its execution isn't mandatory to keep L2J setups working past any core revision
number. (e.g. orphans cleanup)

- Its execution were time consuming and could slowdown regular database update tasks.
(e.g. complex sub/queries, joins)

- Its execution could allow administrators to perform optimization, maintenance, 
repair or recovery tasks whenever they needed to.

Any SQL maintenance should be named like that:

YYYYMMDDmaintenance(_s).sql

See the updates directory documentation for further details of the naming convention.

Additionally, it would be desirable that any maintenance script could hold internal
documentation describing their specific purpose, execution scenario and any other
information that could be of interest for the administrator.