We are running GG MA 19.1 and are migrating from 18c on exadat to 19c on a new exadata. We are using GG to migrate to the new hardware. We have a DB that has a table that gets edited quite a bit. We set up the extract and pulled the SCN from that. Then we did an expdp by scn for an initial load to the new hardware. This is a DB of about 1TB so it took a few hours to fully export and import but it went successfully. After the import ended we started the replicat by using after aftercsn to match our SCN from the initial extract start. Well, the replicat immediately. abended. It was trying to update a record that wasn't in the target. We had to enter the lines in the replicat handlecollisions and insertmissingupdates. Now I read all of the notes to take that out as soon as possible and once the lag caught up we did remove that. Everything seems fine but I am concerned what we did wrong? Shouldn't the fact that we did all of this by SCN it should all line up. Any thoughts would be great. Thanks.