Sun Java System Messaging Server 6.3 Administration Guide Full and Incremental Backups

Incremental backups (see Incremental Backup) will scan the store for changed data and back up only what has changed. Full backups will back up the entire message store. You need to determine how often the system should perform full as opposed to incremental backups. You’ll probably want to perform incremental backups as a daily maintenance procedure and full backups once a week.