Available with Standard or Advanced license.
The raster pyramids or statistics associated with raster datasets in the mosaic dataset item do not reside in the same location as the corresponding raster dataset.
The supporting files that contain pyramids and statistics are stored in a different location from the source data. This often occurs when pyramids or statistics are created within a read-only folder. The supported files cannot be written back to the read-only folder, so they are stored in the raster proxy folder instead.
There is no solution for this issue, unless pyramids and statistics are calculated again while the folders have write permissions.