Limitation on NDF or HDS file sizes

The Starlink NDF format is a special case of the HDS (Hierarchical Data System; see SUN/92[32]) format. There is currently a fundamental limitation of HDS which will be corrected in a future release. Until then, there is a problem with HDS files longer than 512Mbyte. Such files can result either from a user NDF file which is very long (for example, a 9000x9000 type _REAL frame with variances) or, more likely, from a file used as temporary workspace by CCDPACK or other applications.

This problem may not be reported as such by the software, but often manifests itself as an `Object not found' error, which will cause the application to terminate. In this case there is not much which can be done apart from discussing the matter with the programmer responsible for supporting the package.