After a second thought, I think the warning should be printed anyways when CLOCK versioning mode is used because it does not guarantee happens-before relationship when cache operations are invoked on different nodes (see an example in pseudo-code below). Essentially, when cache operations are invoked on different nodes within a time span smaller or equal than time sync error, they are considered to be run concurrently.
IgniteCache cache = ignite.cache("name"); cache.put(1, 1); // Select a random remote node. ClusterGroup grp = ignite.cluster().forRemotes().forRandom(); ignite.compute(grp).call(new Callable() { public Object call() throws Exception { cache.put(1, 2); // This does not guarantee to succeed in CLOCK mode. } }); // This may fail in CLOCK mode. assert cache.get(1) == 2; I agree that the documentation must be updated accordingly, and I think the warning printed should contain a link to the page. Any other thoughts?