Only write, not rewrite

[bemulima]

I have a relation (has many) model and when saved common model I would like SaveRelationsBehavior only write new record to db. Now SaveRelationsBehavior every time rewriting relations data. This my behavior in model:

public function behaviors() {
        return [
            [
                'class' => SaveRelationsBehavior::class,
                'relations' => [
                    'vacancies',
                    'resumes'
                ],
            ],
        ];
    }

So, how can I do to only writer SaveRelationsBehavior?