Immutable storage for Azure blob that enables users to store business-critical data in a WORM (Write Once, Read Many) state.

Immutable storage supports two types of policies:

Time-based retention

Time-based retention allows users to add policies and store data for a specified interval between 1 day and 400 years.

Time-based retention policy is used to lock data from future edits, once the policy is locked, it cannot be unlocked.

Legal hold

Legal hold each legal hold policy needs to be associated with 1 or more tags. Tags are used as a name identifier, such as a case ID or event name. When a legal hold is in effect, blobs can be created and read, but not modified or deleted

Legal hold is set the data in all the blobs of the container moves to a delete-protected and modify-protected state.

Note- Retention policy changes may require some time to take effect.

You cannot delete or modify any files with the container whilst there is either a Time-based retention policy or a Legal hold policy.

Select from Azure Portal

You could click left hand menu item Storage account → Containers → Select after creating new Container → Access policy

Time-based retention

You can add a number of days value between 1 day and 400 years, this applies to files immutable. .

The time interval in days that the data needs to be kept in a non-erasable and non-modifiable state. Upon the expiration of the retention interval, the data will continue to be in a non-modifiable state.

Once the policy is locked, the container cannot be deleted or edit, and the storage account cannot be deleted until the retention period is over.

Tips: You cannot change this value to 0 at any time. Once the interval you add expires – Upon the expiration of the retention interval, the data will continue to be in a non-modifiable state but can be deleted. Retention policy changes may require some time to take effect. 5 edits are permitted to the policy.

Please refer Immutable storage for Azure blobs.