(j3.2006) Connecting more than one unit to a file

[Bill Long]

On Oct 30, 2015, at 3:31 PM, Van Snyder <Van.Snyder at jpl.nasa.gov> wrote:

> 9.5.4p4 says it is processor dependent whether more than unit can be
> connected to a file.
> 
> 9.5.6.1p8 prohibits it.
> 
> Since the permission in 9.5.4p4 is new, and is newly remarked in A2, we
> can assume that not changing the prohibition in 9.5.6.1p8 to a processor
> dependency was an oversight.

Looks that way.  How about changing:

"If a file is already connected to a unit, an OPEN statement on that file with a dierent unit shall not be executed."

to either nothing (delete the sentence), or

?If a file is already connected to a unit, the effect of executing an OPEN statement on that file with a different unit is processor dependent.? {And add a line in Annex A}

> 
> Assuming we wish to allow multiple units to be connected to a file, do
> we need further explanation of how nonadvancing and asynchronous output
> work if they are done simultaneously on more than one unit connected to
> the same file?

We wish to allow vendors to allow this (which some already do).  Beyond that, we didn?t intend to be more specific.  As a practical matter, allowing multiple units (normally one per image) to connect to a file is much simpler if the file is open on all of the units for reading only.  This is operationally similar to multiple independent programs opening the same file for read-only, which has been going on for years.   Coordinating output to the same file is harder.  Vendors are free to prohibit output as part of the ?processor dependent? umbrella.

Cheers,
Bill

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Bill Long                                                                       longb at cray.com
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