Develop a SecurityRealm plugin

Now, I want to develop a plugin for SecurityRealm extension.
Here is my purpose, use external authentication, eg . use my own account system. and then save the users into jenkins database.
so, a user first login then redirect to my account system. later, as the users have been saved, the login would not be redirect any more.
my question: is it necessary to save the users into jenkins database? if not, the other plugins which need the users information will be affected?