One of my clients is restoring their database backup to another server for some testing. They do it periodically so we can also verify that the backup is good (which is great!). In a few cases, after the restore I saw that the restored database has an incarnation that the original database doesn’t have (and not the one created by the “open resetlogs” after the recovery). This actually caused a problem during the restore, but this restore has a few issues (I started a post about that as well).
After opening an SR about that, the engineer said that Oracle automatically catalogs any archive logs located in the FRA and have the same DBID. In my case, we use the same server each time we restore a database. Before I restore the database I drop the old one (using “drop database”), but I see some orphan archive logs in the FRA (ASM in my case). I didn’t care about them until now, but apparently Oracle sees them, registers them in the control file and creates another database incarnation because of that.
If you do the same, make sure there are no archive logs in the FRA before restoring the database.