Retention
Objects have a retention property that determines how long the object must remain in the namespace before it can be deleted. This time can range from allowing the object to be deleted at any time to preventing the object from ever being deleted. While an object cannot be deleted due to retention, it is said to be under retention.
If an object is immediately placed under retention when it is stored, it is stored with no POSIX write permissions. When an existing object is placed under retention, its POSIX write permissions are removed.