The Calendar Server system records each transaction for the calendar database (additions, modifications or deletions to calendars and their properties) in a transaction log file. At some predetermined interval, the log file is closed for writing and another is created. The system then applies the transactions from the oldest closed transaction log to the live calendar databases as time permits. When all the transactions in the log have been applied to the database, the log is marked as “already applied”.
When hot backups are configured, a snapshot of the live databases is taken every 24 hours. The already applied logs are then applied to the hot backup copy of the databases. The hot backup databases are as current as the number of transactions still waiting to be applied.