How to change a memory-resident TTree into disk-resident?

Just open the object and rewrite it into the disk?
But my PC’s memory is limited and the TTree is too big to be loaded into the memory once. :frowning:
Is there a easy way to do this?

No. By definition a memory-resident ntuple must fit in memory.



Not sure I understand - are you trying to create this TTree ? and when you run whatever program you use to do it, it crashes for lack of memory before finishing filling the TTree with all your data ?

If so, you could try writing the TTree to disk as you go, so that the amount of it in memory is never greater than your limit. Or maybe write several files containing identical TTrees each containing a manageable amount of data - then use a TChain to analyse them ?

Or am I completely barking up the wrong TTree ? :laughing: