I found a related a posting, Increased system keyspace size after backups finish - #6 by SteavedHams
From reading the posting, it seems the system keyspace for backup (and DR, I believe) would contain the backup status data and backup snapshot file map.
We are just wondering if it would contain any transaction log entries (Some DBMSs do that). We are setting up DR for production, so the size increase is a concern for us.
We are using FDB v6.2.27.
Thanks.