Re: [Pytables-users] Danger of file corruption? (was: Bug? flush() ignores new tables)

[Norbert N. <Nor...@gm...>]

On Thursday 30 September 2004 09:56, Francesc Alted wrote:
> A Dijous 30 Setembre 2004 09:32, Norbert Nemec va escriure:
> > Even though: I would strongly hope that it is not necessary. Does
> > h5file.close() do anything on the file but flush() it and then close the
> > physical file? In other words: is there any danger of file corruption if
> > the python program is just shut down cold without a chance to save
> > anything? Like - when the file is written via NFS and the computer
> > running the program is switched off hard?
>
> I'm not completely sure, but muy guts say that this would not be a problem.
> If your program crashes (or is shut down) and there are buffers that are
> not written yet, then the file will miss this information, but will not get
> corrupted.
>
> The only problem may appear if you shut down the program *during* a write
> process. In that case I guess you will end with a corrupted file, as there
> are no provision of I/O transactions yet.

OK, that leaves me two specific questions:

* Does pytables ever initiate writes except in explicit flush() and close() 
commands?

* Are the elementary operations of the underlying hdf5 library atomic? I.e.: 
If I shut down the program in the middle of a pytables write action, might 
the resulting file be fundamentally corrupted at the hdf5 level, or would the 
corruption be well localized and reparable?

All leading to the third question:

* Might there be some simple way to make a set of changes atomic? Even if that 
means restricting the use of pytables?

Ciao,
Nobbi

-- 
_________________________________________Norbert Nemec
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