[Info-vax] OpenVMS - file selection abnormally with Copy / Rename or user ignorance?

[Stephen Hoffman]

> On Fri, 27 Mar 2015 20:02:18 -0700 (PDT), IanD
> <iloveopenvms at gmail.com> wrote:

In addition to the version number — which in this case tells us this is 
OpenVMS Alpha.  Please (always) post the exact commands and the exact 
error messages involved; post the source code reproducer.  The source 
code here is the DCL commands.    Certainly obfuscate the filenames if 
and as necessary, but please don't paraphrase the details of the 
commands and the error messages.

Related: <https://mikeash.com/getting_answers.html>

On no evidence (and unfortunately), this case could well be fallout of 
the "VMS is painfully slow dealing with them, but that's another 
matter" problem.  Having tens of thousands of files in a directory is a 
design that just doesn't scale well and doesn't work well on VMS.    
Split those directories on an hourly or daily basis, depending on the 
application.  Don't try to store tens of thousands of files in one 
directory, particularly if those files are actively churning.   Access 
to the date and other metadata is via the file header which is going to 
be slow(er), and a directory file that's churning will be locking and 
unlocking as the files are added or removed from the directory.  The 
directory shuffling is better in recent releases, but there's still 
contention — this is the origin of the reverse delete mechanism that 
some folks use.

FWIW, BACKUP /IGNORE=INTERLOCK — if that's what you are using — does 
not reliably report collisions and does not produce consistent output 
data, particularly in a cluster.  Those interlocks are there for a 
reason, after all.




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