Billy Ashton asked how to do the equivalent of a USS "touch" on a z/OS data set.

I'm wondering if there's something like the C "DD:ddname" filename 
specification hack that could be used. I know this would seem odd: run a batch 
job that uses BPXwhatever to run USS "touch", but if it's possible...?

This makes me realize that I don't know what "touch" actually does. I mean, I 
know the effect, but what does it have to do to make that happen? If it's some 
filesystem function, a minimal C program might be able to use the "DD:ddname" 
hack and that function. Googling suggests that it just opens the file and that 
that's sufficient to update it, but there has to be more, since it can 
optionally update just the last access time, without updating the last changed 
time.

In fact, the more I think about this, I now wonder what "last referenced" even 
means; I assume it's time of last access, not change?

Billy wrote, in part:
> We don't want to do things like allocate, open, and print one record, 
> as some of these files are huge (25-50GB).

Would you need to print a record to update "last referenced"? Shouldn't reading 
a record suffice? Do you even need to do that? Why does the size of the file 
matter here?

I'm sure these are dumb questions but my in-depth filesystem knowledge is for 
other OSes, so I'm just knowledgeable enough to be curious...

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