If an identifier for an NDF section is supplied to this routine, then the returned locator will refer to the associated base NDF.
It is the caller
’s responsibility to annul the locator returned by this routine (by calling the HDS routine
DAT_ANNUL) when it is no longer required. The NDF_ system will not perform this task
If this routine is called with STATUS set, then an invalid locator will be returned for the LOC argument, although no further processing will occur. The same value will also be returned if the routine should fail for any reason.
Although this routine will check the access mode value supplied against the available access to the NDF, HDS does not allow the returned locator to be protected against write access in the case where WRITE access to an NDF is available, but only READ access was requested. In this case it is the responsibility of the caller to respect the locator access restriction.
The locator returned by this routine should not be used to make alterations to any part of a data structure which is simultaneously being used by the NDF_ system, otherwise there is the possibility of serious internal errors and data corruption.