Thank you Kanade and Rob. The module I use is module load ansys/fluids_19.2. So the version is R19.2.nWhen I can't read it in 40 cores, somehow I can read dat.gz file with 6GB in 80 cores. But I can't request more CPU resource; 40 cores to run two weeks is my quota. Now I have to run the case day by day in order to request 80 cores. nThe case has run on HPC, and files are saved on HPC; I think it is local drive.nSince I doing coal combustion with DPM model, the number of particles at flow time 1.6 s is about 15 million. each time step, 9400 particles are injected into the burner. it is one of the reasons that file size keeps growing.