You can use the Options tab of a job to set the Backup mode for any type of backup jobs: full, incremental, differential or copy. For scheduled automatic rotation jobs, Yosemite Server Backup automatically updates this job setting to the value indicated on the Schedule tab of the job.
When the Backup mode is set to Full, all files selected are backed up, including the entire information store and directory databases. Transaction logs are also backed up and then purged.
When the Backup mode is set to Incremental, only changes that have occurred since the last backup job are backed up. In particular, for databases, only the .log files are included in the backup job.
When the Backup mode is set to Differential, for databases, only the .log files are included in the backup job, but these files are not purged.
When the Backup mode is set to Copy, Yosemite Server Backup runs the job similar to full backup. However, the transaction logs are not purged at then of a job run in Copy mode.
Backup Modes and Circular Logging
Microsoft Exchange Server supports database circular logging. Circular transaction logs differ from normal logs in that only a few log files are maintained. These files are purged automatically as new log files are created. When the transactions in the circular log files are recorded in the database, the log files are then deleted. New transactions are recorded in newly created log files.
If circular logging is enabled, you cannot do incremental or differential backups. These backup modes rely upon past transaction logs and thus are not available when circular logging in enabled. When circular logging in enabled, Yosemite Server Backup will revert to full backup mode.
You can check to see if circular logging in enabled for a particular server by examining the Advanced tab of that server’s Properties window. If you turn circular logging off, Microsoft Exchange Server will stop the database service and restart it after making the changes.