Unexpected behaviour of rootrm!

I am removing half of the trees from a root file using the command rootrm.
I checked the size of the file before and after I remove the trees and it is the same, 728 MB

I checked the file using rootls and I see that the trees are removed.

is not strange that the file has the same size? in principle the size should be reduced by 50%


ROOT files are NEVER “physically shrank”.
You need to copy (e.g. using “rootcp”) objects, that you want to keep, to a completely NEW file (which will then be smaller than the original file).