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A Note on Modes of Access  

When obtaining an NDF identifier for a data structure using NDF_FIND, the NDF library has to decide what mode of access to grant (i.e. whether it should allow the NDF to be modified or whether it should be ``read only''). It normally does this by inspecting the locator supplied and permitting modification of the NDF only if the locator itself permitted modification of the data structure. Access can subsequently be further restricted, if required, using NDF_NOACC (see §[*]).

However, if the locator supplied has the value DAT__ROOT (indicating that an absolute NDF name has been given), then this method cannot be applied. In this case, read only access will be obtained by NDF_FIND and subsequent modification of the NDF will not be permitted. If the ability to modify the NDF is required, the routine NDF_OPEN should be used instead, as this allows the access mode to be specified (see §[*]).



next up previous
Next: Obtaining an HDS Locator for an NDF
Up: CONNECTING WITH THE DATA SYSTEM
Previous: Finding and Importing NDFs


Starlink User Note 33
R.F. Warren-Smith
11th January 2000
E-mail:rfws@star.rl.ac.uk

Copyright © 2000 Council for the Central Laboratory of the Research Councils