https://www.cisco.com/en/US/docs/storage/san_switches/mds9000/sw/rel_3_x/configuration/guides/fm_3_3_1/p Port Security Activation By default, the port security feature is not activated in any switch in the Cisco MDS
9000 Family. By activating the port security feature, the following apply: Auto-learning is also automatically enabled, which means: From this point, auto-learning happens for the devices or interfaces that were already logged into the switch and also for the new devices will login in future. You cannot activate the database until you disable auto-learning. All the devices that are already logged in are learned and are added to the active database. All entries in the configured database are copied to the active database. After the database is activated, subsequent device login is subject to the activated port bound WWN pairs, excluding the auto-learned entries. You must disable auto-learning before the auto-learned entries become activated.