What did pax romana mean when the temple doors of janus were opened?

The two doors of the temple of Janus (the two-faced good of beginnings and transitions, gates, doors, passages, endings and time) which were called the Gates of Janus, were closed in times of peace and opened in times of war.

The closing of the doors of the temple were closed very rarely. It happened for the first time under king Numa Pompilius (715-673 BC). The second time was under Titus Manlius in 235 BC. They were closed three more times under Augustus in 29 BC, 25 BC, and possibly 13 BC. The sixth time was under Nero in 66 AD and the seventh time under Vespasian in AD 70. It is likely that Trajan and Hadrian and Antoninus Pius each closed the Gates of Janus once.

The term Pax Romana (Roman Peace refers to a 206-year period of relative political stability within the Roman Empire, not the absence of war. During this period Rome fought wars with many peoples outside the empire and the period saw the last phases of imperial expansion. During the Pax Romana Rome conquered north-western Spain, Moesia, Rhaetia, Noricum, Pannonia, Mauretania, England and Wales, and Dacia. Thrace, Pamphylia, Lydia and Nabataea were annexed. There were also wars with the Marcomanni and the Persians.