Generally available: Immutable storage for Azure Data Lake Storage
Immutable storage for Azure Data Lake Storage is now generally available. Immutable storage provides the capability to store data in a write once, read many (WORM) state. Once data is written, the data becomes non-erasable and non-modifiable and you can set a retention period so that files can't be deleted until after that period has elapsed. Additionally, legal holds can be placed on data to make that data non-erasable and non-modifiable until the hold is removed.
This release includes the new “allow append writes for block and append blobs” flag, which allows users to set up immutable policies for block and append blobs to keep already written data in a WORM state and continue to add new data.
If you are using NFS 3.0 protocol or SFTP support on an account, immutable storage is not supported.
Source: Generally available: Immutable storage for Azure Data Lake Storage