Hi Felix,
You have two possibilities
-1: call tree.AutoSave at regular intervals
-2: use the following procedure
tree.AutoSave
delete file
TFile *file = new TFile("myfile.root","update");
TTree *tree = (TTree*)file->Get("tree");
loop on tree->Fill
etc..
Rene Brun
On Wed, 20 Nov 2002, Eftychios Matathias wrote:
>
> Dear all,
> first of all this is my first message to the roottalk list although I have
> been using root for a couple of years now. My name is Felix Matathias and
> I am a grad student at the Relativistic Heavy Ion Group at the
> State University of New York at Stony Brook and a member of the PHENIX
> collaboration. Enough said :) Root Rocks!
>
>
> To the problem now:
> I have an online monitoring program, always running, that periodically
> writes an ntuple to a file. I open the file, write the ntuple,
> close the file, reset the ntuple, fill new data and the loop continues.
>
> The problem is that even if I open the file to write in UPDATE mode the
> ntuples are written as diffenent keys/objects instead for a single merged
> ntuple. And therefore a user cannot operate at the prompt and draw the
> entire history.
>
> Is there a way of avoiding this ?
>
> I am familiar with the way to retrieve all the keys and merge them into a
> single Ntuple etc. but I was wondering if root can do such a thing
> automatically. I am considering doing the Autosave()/SaveSelf() trick but
> I am a bit nervous having a file open for such a long period of time.
>
> Best Regards,
> Felix
>
>
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