
Trnres00001.jrs and Trnres00002.jrs: These reserve transaction log files act as placeholders.This file is always in the same location as the mail.que file. Trn.chk: This checkpoint file tracks the transaction log entries that have been committed to the database.Trntmp.log is then renamed Trn.log and becomes the current active transaction log file. If the existing Trn.log transaction log file reaches its maximum size, Trn.log is renamed to Trn nnnn.log, where nnnn is a sequence number.

Trn.log is the current active transaction log file. Trntmp.log is the next provisioned transaction log file that's created in advance. Changes to the database are first written to the transaction log and then committed to the database.

Mail.que: This queue database file stores all the queued messages.Under the folder location " %ExchangeInstallPath%TransportRoles\data\Queue", there are five types of queue database files( Queue database files):
