That is more or less how Oracle does commit and rollback: changed items create a version in a "rollback segment". Queries begun during a transaction's life will

That is more or less how Oracle does commit and rollback: changed items create a version in a "rollback segment". Queries begun during a transaction's life will get the original version of the changed items there. One can run out of rollback space, and so cause a transaction to be aborted before it creates potential inconsistency, though I haven't seen that happen in years. I can't comment on the legal stuff. But I don't think that Oracle was the only one to manage "read committed" consistency this way.