R/telemetry.R
h2o.set_telemetry.RdApplies immediately for this R session and is remembered across sessions
(stored under ~/.h2oai). The DO_NOT_TRACK environment variable
still overrides it. Persistence is best-effort (disk errors are swallowed);
a non-logical enabled raises an error rather than being guessed.
h2o.set_telemetry(enabled)(invisibly) TRUE if the preference was written to disk, else FALSE.