Many copies of a file open on many machines and TCollections

If I want to update many objects stored in the same TFile in the same TCollection using multiple machines (no more than say five at a time), how can I do this without risking overwriting one object with an old version when I save another object?

What is the best way to do this?

“Saving Histograms to Disk” makes it sound like I can write single onbjects to file at a time without effecting the other objects. However, I am not sure how the file is actually written. Will the objects that were placed into memory written as they appeared in the TFile at that moment or when the file was first opened(seems unlikely, but I would like to be certain). If the file is large and the computer is under heavy load, it is concievable that even this would cause problems.

Would it be best to save each altered object with a different cycle number and church it up later(i update a time stamp on each object)?