Apache Directory Server doesn't appear (from the currently incomplete documentation) to have any integrated backup and restore mechanism.
In this scenario you could do a couple of things:
Stop the LDAP server before backing up its files, then restarting. This involves downtime though.
Take a snapshot of the filesystem and backup the snapshot. Obviously this depends upon what filesystem is in use. It also depends upon ADS being able to recover when starting with files that were in use at the time of the backup.
Apache Directory Server doesn't appear (from the currently incomplete documentation) to have any integrated backup and restore mechanism.
In this scenario you could do a couple of things: