I want to filter an TTree to save in a new root file only events that pass a particular selection. I’m new in the manage of TFile, TProofOutputFile with Proof and I’m experiencing a problem with my code and I’m able to reproduce it with the tutorial ProofNtuple.C. Our proof cluster consist of 3 nodes: t2-wn-9, t2-wn-10, t2-wn-11. I’m logged into t2-wn-11.

```
.x $ROOTSYS/tutorials/proof/runProof.C+("ntuple(nevt=10000000)", "localhost")
Warning in <ACLiC>: /gpfs/storage_4/users/home/proof/root/tutorials/proof is not writeable!
Warning in <ACLiC>: Output will be written to /tmp/turra
Starting master: opening connection ...
Starting master: OK
Opening connections to workers: OK (24 workers)
Setting up worker servers: OK (24 workers)
PROOF set to parallel mode (24 workers)
getProof: WARNING: started/attached a session on external cluster (localhost): 'dir="/tmp/turra/.proof-tutorial"' ignored
runProof: ntuple: ACLiC mode: '+'
runProof: running "ntuple" with nevt= 10000000
Warning in <ACLiC>: /gpfs/storage_4/users/home/proof/root/tutorials/proof is not writeable!
Warning in <ACLiC>: Output will be written to /tmp/turra
TProofOutputFile::AddFile: error from TFileMerger::AddFile(root://t2-wn-09.mi.infn.it//proof/workingdirs/turra/session-t2-wn-11-1282728816-12862/worker-0.3-t2-wn-09-1282728819-14123//SimpleNtuple.root)
TProofOutputFile::AddFile: error from TFileMerger::AddFile(root://t2-wn-09.mi.infn.it//proof/workingdirs/turra/session-t2-wn-11-1282728816-12862/worker-0.21-t2-wn-09-1282728821-14130//SimpleNtuple.root)
TProofOutputFile::AddFile: error from TFileMerger::AddFile(root://t2-wn-09.mi.infn.it//proof/workingdirs/turra/session-t2-wn-11-1282728816-12862/worker-0.15-t2-wn-09-1282728821-14132//SimpleNtuple.root)
TProofOutputFile::AddFile: error from TFileMerger::AddFile(root://t2-wn-09.mi.infn.it//proof/workingdirs/turra/session-t2-wn-11-1282728816-12862/worker-0.12-t2-wn-09-1282728818-14118//SimpleNtuple.root)
TProofOutputFile::AddFile: error from TFileMerger::AddFile(root://t2-wn-09.mi.infn.it//proof/workingdirs/turra/session-t2-wn-11-1282728816-12862/worker-0.6-t2-wn-09-1282728820-14125//SimpleNtuple.root)
TProofOutputFile::AddFile: error from TFileMerger::AddFile(root://t2-wn-09.mi.infn.it//proof/workingdirs/turra/session-t2-wn-11-1282728816-12862/worker-0.0-t2-wn-09-1282728818-14120//SimpleNtuple.root)
TProofOutputFile::AddFile: error from TFileMerger::AddFile(root://t2-wn-09.mi.infn.it//proof/workingdirs/turra/session-t2-wn-11-1282728816-12862/worker-0.9-t2-wn-09-1282728821-14128//SimpleNtuple.root)
TProofOutputFile::AddFile: error from TFileMerger::AddFile(root://t2-wn-09.mi.infn.it//proof/workingdirs/turra/session-t2-wn-11-1282728816-12862/worker-0.18-t2-wn-09-1282728823-14134//SimpleNtuple.root)
TProofOutputFile::AddFile: error from TFileMerger::AddFile(root://t2-wn-10.mi.infn.it//proof/workingdirs/turra/session-t2-wn-11-1282728816-12862/worker-0.4-t2-wn-10-1282728820-14049//SimpleNtuple.root)
TProofOutputFile::AddFile: error from TFileMerger::AddFile(root://t2-wn-10.mi.infn.it//proof/workingdirs/turra/session-t2-wn-11-1282728816-12862/worker-0.1-t2-wn-10-1282728819-14047//SimpleNtuple.root)
TProofOutputFile::AddFile: error from TFileMerger::AddFile(root://t2-wn-10.mi.infn.it//proof/workingdirs/turra/session-t2-wn-11-1282728816-12862/worker-0.10-t2-wn-10-1282728822-14056//SimpleNtuple.root)
TProofOutputFile::AddFile: error from TFileMerger::AddFile(root://t2-wn-10.mi.infn.it//proof/workingdirs/turra/session-t2-wn-11-1282728816-12862/worker-0.19-t2-wn-10-1282728821-14054//SimpleNtuple.root)
TProofOutputFile::AddFile: error from TFileMerger::AddFile(root://t2-wn-10.mi.infn.it//proof/workingdirs/turra/session-t2-wn-11-1282728816-12862/worker-0.16-t2-wn-10-1282728819-14045//SimpleNtuple.root)
TProofOutputFile::AddFile: error from TFileMerger::AddFile(root://t2-wn-10.mi.infn.it//proof/workingdirs/turra/session-t2-wn-11-1282728816-12862/worker-0.22-t2-wn-10-1282728818-14042//SimpleNtuple.root)
TProofOutputFile::AddFile: error from TFileMerger::AddFile(root://t2-wn-10.mi.infn.it//proof/workingdirs/turra/session-t2-wn-11-1282728816-12862/worker-0.7-t2-wn-10-1282728820-14051//SimpleNtuple.root)
TProofOutputFile::AddFile: error from TFileMerger::AddFile(root://t2-wn-10.mi.infn.it//proof/workingdirs/turra/session-t2-wn-11-1282728816-12862/worker-0.13-t2-wn-10-1282728816-14040//SimpleNtuple.root)
Mst-0: merging output objects ... done
Output file: /gpfs/storage_4/users/home/turra/ProofNtuple.root
Mst-0: grand total: sent 9 objects, size: 634564 bytes
outputFile: /gpfs/storage_4/users/home/turra/ProofNtuple.root
Managed to open file: /gpfs/storage_4/users/home/turra/ProofNtuple.root
```

At the end the file is merged but with only 1802988 events instead of 10000000. If you look at the warning the problem is that the client t2-wn-11 is unable to find files on the other workers.

With prooflite I don’t have the problem