A globally unique identifier for the backup which cannot be changed. Values are of the form projects/<project>/instances/<instance>/backups/[a-z][a-z0-9_\-]*[a-z0-9] The final segment of the name must be between 2 and 60 characters in length.
The backup is stored in the location(s) specified in the instance configuration of the instance containing the backup, identified by the prefix of the backup name of the form projects/<project>/instances/<instance>.
Required. A mask specifying which fields (e.g. expireTime) in the Backup resource should be updated. This mask is relative to the Backup resource, not to the request message. The field mask must always be specified; this prevents any future fields from being erased accidentally by clients that do not know about them.
This is a comma-separated list of fully qualified names of fields. Example: "user.displayName,photo".