Make a huge root file

Dear experts,
I have many root file with a total of 300GB. When I merge at then end it does not work, probably the merge file become too big. Do you know how I can do that?
Regards

See https://root.cern.ch/doc/master/classTTree.html#a3ab4006402ddbc3950e1ddab5e3aadd6

The better answer is actually a question: Why would you want to do that?! I’d recommend ~500 MB to 1 GB per file. See also Can I disable the maximum root file size?

Dear behrenhoff,
well as physicist we manipulate many files right?.. So I need these files.
Regards

Dear Behrenhoff,
is it possible to disable the maximum root file size while doing “hadd file.root huge1.root huge2.root”? or should I wrote a code?
Regards

Still, why do you want to join? “I need the files” is not a reason for joining.

What contents do you want to join?

Trees? In that case: just don’t join / or just join a few files! (you can use a TChain)
Histograms? Use hadd -T to exclude trees from the join.

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Dear behrenhoff,
I have many root files in a directory, I currently have a code which take 1 root file to plot the tree variables. Maybe I could do a of loop the root file instead of nerging them… Is there an example how to do that?
Regards

See TChain

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Dear behrenhoff and pamputt,

yes “TChain” is the best option in my case. Thank you for your help.

Regards

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