This informational message indicates that the specified index cannot be checked because one of the filegroups that stores data for the index is offline. The state of the files in a filegroup determines the availability of the whole filegroup. To be available, all files within the filegroup must be online. The filegroup that is offline may be for the large binary object (LOB) data, for the row-overflow data, or for the data itself. If there are no other problems, all other indexes for the same table are checked.