It should work for both retention mode — Enterprise and Compliance.
First of all you need to delete all of content for NS. Its not enought to delete it via web interface because you can not delete folders (for example), metadata and different versions which was created by versioning
To delete some content its better to use S3 browser, but when you want delete entiry namespace the error is displayed
Then you need to:
1. In Policies — Versioning — disable versioning by clear checkboxes «Enable verisioning», «Keep deletion records for versioned objects» and keep checkbox «Prune versions older than 0 (zero) days»;
2. In Services — Replication — disable replication for this namespace by clear checkbox «Enable replication»;
3. In Services — Search — disable search by by clear checkbox «Enable search»