Warning - possible pitfall:

A case which occasionally causes problems can arise if a primitive NDF is created (e.g. by calling NDF_CREP - see §) and an array component is then mapped for access using an access mode such as `WRITE/ZERO'. This access mode will cause the component's bad-pixel flag to be set to .FALSE. (see §). When the component is unmapped, this, in turn, will cause its storage form to be implicitly converted to simple.

This behaviour is correct, but it is not always what is expected, or wanted. It can be avoided by setting the bad-pixel flag value back to .TRUE. (see §) before unmapping the component concerned, or by performing the initialisation to zero explicitly rather than via an initialisation option on the mapping mode.