Re: [ROOT] Merging files

From: Christian Schmitt (schmittc@whep.uni-wuppertal.de)
Date: Thu Nov 29 2001 - 16:30:15 MET


Maybe I should clarify what I want to do:

I have several hundreds of files which is quite a mess to handle. Therefore I 
want to merge them.
As the total size is roughly 10GB I cannot merge them into one file (because 
of the 2GB limit).
So I wanted to reduce the number of file to roughly 5 or 6 (which then for 
the processing will be added to a chain of course).

This would help me a lot when doing a bookkeeping of my files. I know that in 
principle I can do this by hand: merge files wich together have a size of 
less than 2GB and repeat this step 5 to 6 times.
But I will have to do this every month or even more frequently and so I hoped 
it would be possible to have a more automatic machinery for this.

Regards,

	Christian


> Christian: the whole point of TChain is to allow processing of the data
> volumes above 2 GBytes. TChain doesnt' merge the files physically - it is a
> list of files, so 2 GByte limit doesnt' exist for it. The bottom line:
> either TChain::Merge or TChain::Add will do.
> 								- best, Pasha
>
> Christian Schmitt wrote:
> > Hi ROOTers,
> >
> > I have the following problem: I need to merge several hundred files, each
> > containing the same tree. The total size is something like 10 GB.
> > So I cannot use just TChain::Merge because of the 2GB limit of
> > root-files.
> >
> > Now my wuestion is: how can I merge the files such that ideally I get 5
> > to 6 files with each having a filesize < 2GB ?
> >
> > It should be a solution which works in general, i.e. doesn't make an
> > asumption on the structure of the tree in the files (the only thing known
> > is that the trees are simple trees, i.e. only integers, or floats are
> > stored).
> >
> > Thanks for your help,
> >
> >         Christian Schmitt



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