Legacy DNSSEC on UltraDNS required a re-signing after every change made to the zone file to insure validation continued. On-The-Fly signing eliminated that necessity. Domains using the legacy signer (signified with type-8 DS RRs/DNSKEYs) should be migrated over to On-The-Fly signing for quality of life improvements and in preparation of the legacy signer's sunsetting.
The DNSSEC Migration Tool is available to all accounts. Once a user is logged in they will modify the URL in their browser's address bar to the following:
Timing of the steps is important to avoid potential validation errors during the rollover process. The tool both notes the times and tracks how long since it performed the previous step. A warning will be displayed if attempting to move on too soon. Below are screenshots of each step from the migration tool.