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Re: 950209: netCDF on VAX/VMS cluster

>Organization: Accu-Weather
>Keywords: 199502091711.AA25983 netCDF OpenVMS

Hi Bryan,

>                                ...  We are considering using netCDF
> on an Alpha machine using OpenVMS.  The Alpha is part of a cluster
> of Vaxes.  I noticed on page 149 of the NetCDF User's Guide (Version 2.3,
> April 1993), that the default is not to open files for shared access on
> VMS machines.  The application that we are considering NetCDF for will
> need to have shared access.  I would appreciate if you could help me
> with the following questions (or direct me to people who can help me):
> 
> 1)  What kind of performance degradation is suffered on the VAX by opening
>     netCDF in shared-access mode?

It's my recollection that we were unable to get shared access to work at all
under VMS when we last tested it, but that was several years ago.  This
might have been due to a bug in an early version of UNIX stdio under VMS
(before VMS became POSIX -compliant).  Since then we've also changed our
implementation to work on our own I/O layer instead of stdio, so it might
work now.  I'm CC:ing Steve Emmerson on this reply in case he remembers
differently.

> 2)  Are there any people that have tryied to optimize netCDF I/O for the
>     VAX/VMS?

Yes, we had an offer of help with optimizing netCDF for VAX/VMS from Mark
Rivers of BNL <address@hidden>.  I don't know whether he
finished his optimization work and made it available to others.

> 3)  Has anybody ported netCDF to the Alpha running under OpenVMS?

Yes, Joshua Goldstein from Research Systems, Inc. <address@hidden> ported to
Alpha/OpenVMS and offered to give us the changes to integrate back into our
distribution.  I can't locate any changes he may have sent us right now, so
we may not have received them.

--Russ

______________________________________________________________________________

Russ Rew                                                UCAR Unidata Program
address@hidden                                          P.O. Box 3000
http://www.unidata.ucar.edu/                          Boulder, CO 80307-3000
______________________________________________________________________________