I'm going to completely redirect my domainA.com to a domainB.com. I wonder if this will have any effect on SEO of my domainA.com? How will search engines threat it? Won't they ban it because of duplicate content? Or will the domain just be ignored?
As long as the content is only found on domain b, there will be no duplication. Don't expect any SEO of domain A to do much though.
I had a strange experience regarding redirect 2 domains As you said domainA -> domainB , but, sometimes, in google appear or domainA or domainB, and isnt normal to happend !