Hello, Sometime ago I had to solve the problem of writing to common files from parallel R processes. For the synchronization, I created a small package ( https://r-forge.r-project.org/projects/flock/) to perform a lock/unlock between different processes. My feeling is that this is something that belongs to the parallel package. There is at least one other package (synchronicity - http://cran.r-project.org/web/packages/synchronicity/index.html) providing similar (and more) functionality. Regards, Ivan