How to add root files when the target root file is larger than 100 GB

ROOT
2

Hello Arka,
TTree::SetMaxTreeSize should help you with that. Take a look at Root 6.04.14 hadd 100Gb and rootlogon and Hadd: 100Gb TTree Limit/compression levels for extra context and let me know if it helps.
Cheers,
Vincenzo