In message
of087fe71c.cb64f47e-on8525757f.0077b5a9-8525757f.0078f...@us.ibm.com,
Neil Morris morr...@us.ibm.com writes
Hi Mike,
Your inquiry was brought to my attention today.
Could you possibly clarify what is meant by headers are flushed when they
are updated in regard to UniVerse dynamic files? Is this in reference to
the information in the T30FILE structure in the UniVerse disk shared memory
segment being written to the header of the file when an update would result
in changing one of the dynamic file parameters stored in the header? Or
does this comment refer to the updated information in the header of the
file being flushed to the physical disk via a sync operation?
If the former, then it is my understanding that UniVerse has always updated
the header immediately when a dynamic file parameter changed and there is
no specific release in which this capability was added. If the latter, the
only way to force the update to be flushed to disk immediately is to have
the file activated for logging with UniVerse Transaction Logging and have
Checkpoint mode enabled.
Perhaps I'm not understanding the question so any clarification you can
provide would be appreciated.
Hi Neil,
It's long been common knowledge (which doesn't mean it's correct :-)
that UV read the dynamic file parameters into memory when the file was
opened, and didn't always write changed information back until the file
was closed.
You were therefore advised that it was not safe to copy even a quiescent
dynamic file at OS level, because the header and data might not be in
sync.
I remember a posting (from an IBM'er) saying that this had changed round
about rev 10, and that header and data should now always be in sync on
disk. (ie the post was about rev 10, the change might have been earlier.
But the implication was that it *had* been changed.)
Cheers,
Wol
--
Anthony W. Youngman pi...@thewolery.demon.co.uk
'Yings, yow graley yin! Suz ae rikt dheu,' said the blue man, taking the
thimble. 'What *is* he?' said Magrat. 'They're gnomes,' said Nanny. The man
lowered the thimble. 'Pictsies!' Carpe Jugulum, Terry Pratchett 1998
Visit the MaVerick web-site - http://www.maverick-dbms.org Open Source Pick
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