SQL1277W Connection fails because a previous restore operation is still in progress

If you get an SQL1277W after having performed a DB2 redirected restore while trying to connect to the database, one possible cause could be that the backup was taken as a different user (such as root) instead of the instance owner. For databases that use automatic storage, you will likely first get warnings during the restore process saying that tablespaces using automatic storage can get their containers redefined at the end of the restore process.
In short, if you are doing a redirected restore of a database using automatic storage and the restore is not successful completely and you are unable to connect to the db after restoring, it is worth checking if the backup was taken as instance owner or not. Other symptoms could be that one or more tablespaces go offline in drop pending state.