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The routine NDF_TUNE is provided to allow various features of the
NDF_ system to be configured for individual needs if the default
behaviour is not appropriate. This process is referred to as
tuning the system, and is performed as follows:
CALL NDF_TUNE( 0, 'WARN', STATUS )
Here, a new value of zero is specified for the tuning parameter
called `WARN'. The current setting of a tuning parameter may be
determined using the related routine NDF_GTUNE which returns the
parameter's value via its VALUE argument, as follows:
INTEGER VALUE
...
CALL NDF_GTUNE( 'WARN', VALUE, STATUS )
By using these two routines in pairs it is possible to determine the original
setting of a tuning parameter, modify it locally, and then return it to its
original value if necessary.
Each tuning parameter controls one aspect of the NDF_ system's
behaviour according to the value which has been set for it. The tuning
parameters currently available are as follows:
- DOCVT:
-
Controls whether to convert foreign format data files to and from
native NDF format for access (using the facilities described in
SSN/20). If DOCVT is set to 1 (the default), and the
other necessary steps described in SSN/20 have been taken, then such
conversions will be performed whenever they are necessary to gain
access to data stored in a foreign format. If DOCVT is set to 0, no
such conversions will be attempted and all data will be accessed in
native NDF format only.
The value of DOCVT may be changed at any time. It is the value current
when a dataset is acquired by the NDF_ library (or a
placeholder for a new dataset is created)
which is significant.
- KEEP:
-
Controls whether to retain a native format NDF copy of any foreign
format data files which are accessed by the NDF_ library (and
automatically converted using the facilities described in
SSN/20). If
KEEP is set to 0 (the default), then the results of converting foreign
format data files will be stored in scratch filespace and deleted when
no longer required. If KEEP is set to 1, the results of the conversion
will instead be stored in permanent NDF data files in the default
directory (such files will have the same name as the foreign file from
which they are derived and a file type of `.sdf'). Setting
KEEP to 1 may be useful if the same datasets are to be re-used, as it
avoids having to convert them on each occasion.
The value of KEEP may be changed at any time. It is the value current
when a foreign format file is first accessed by the NDF_ library
which is significant.
- SHCVT:
-
Controls whether diagnostic information is displayed to show the
actions being taken to convert to and from foreign data formats (using
the facilities described in SSN/20). If SHCVT is set
to 1, then this
information is displayed to assist in debugging external format
conversion software whenever a foreign format file is accessed. If
SHCVT is set to 0 (the default), this information does not appear and
format conversion proceeds silently unless an error occurs.
- TRACE:
-
Controls the reporting of additional error messages which may
occasionally be useful for diagnosing internal problems within the
NDF_ library. If TRACE is set to 1, then any error occurring within
the NDF_ system will be accompanied by error messages indicating
which internal routines have exited prematurely as a result. If TRACE
is set to 0 (the default), this internal diagnostic information will
not appear and only standard error messages will be produced.
- WARN:
-
Controls the issuing of warning messages when certain non-fatal errors
in the structure of NDF data objects are detected. If WARN is set to 1
(the default), then a warning message is issued. If WARN is set to 0,
then no message is issued. In both cases normal execution continues
and no STATUS value is set.
The value of tuning parameters may also be set by the user of NDF_
applications independently of the application itself. This is
accomplished by defining an environment variable whose name is
constructed by prefixing `NDF_' to the name of the tuning parameter
to be set. Thus, the shell command:
% setenv NDF_TRACE 1
would set the `TRACE' tuning parameter to 1 by default for all
subsequent NDF_ applications (i.e. over-riding the default
described above). The application may, however, still modify the value
itself.
Note that all tuning parameters set in this way must be given valid
integer values. If the associated environment variable does not
translate to a valid value, the default will remain unchanged.
Next: COMPILING AND LINKING
Up: MISCELLANEOUS FACILITIES
Previous: Message System Routines
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