Browse your PhpMyAdmin Database.
Click your Database Name 



then check all Table List Bellow.
========================================================
acc_reg_num
acc_reg_str
achievement
atcommandlog
auction
cart_inventory
cashlog
char
charlog
char_reg_num
char_reg_str
chatlog
guild
guild_alliance
guild_castle
guild_expulsion
guild_member
guild_position
guild_skill
guild_storage
hotkey
inventory
login <--- this table is depend on your required if you dont want to wipe all account registered just leave it dont truncate 
loginlog
mail
mail_attachments
mapreg
market
memo
mvp_ladder_rank
picklog <--- this table will required to truncate every time you perform a maintenance.
storage
vendings
vending_items
zenylog
========================================================

Just truncate/Empty the tables.