Look at what Aleksandr Solzhenitsyn wrote in The Gulag Archipelago about the “mobility” of prisoners in slave-labor camps:
However, for the state there was no economic nor organizational sense in carrying out all this superfluous shifting about of some people from camp to the front, and some people to camp in their place. Everyone had had his own circle of life and death determined for him: Once you’ve been classified among the goats, then you have to die as a goat. Sometimes they did not take nonpolitical offenders with short terms for the front, and not in penalty companies, of course, just in the ordinary active army.
The Gulag Archipelago, Volume 2, p 135