File Read in 2 JVM

I am going to read file in one JVM that someone create in another JVM.
Writer JVM is older class, but I can ask them to modify it for me.

This is in linux.

I am worried about dirty reads. Reading the file when writer JVM is not
done writing. What is good way to handle this? The file is huge (like
40-60 gigs) and will not fit in memory.

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