How to set PostgreSQL's permission when migrate other database to it on AWS?

We want to migrate an Oracle DB to a PostgreSQL DB in RDS with DMS. There is an official guide for preparision in the PostgreSQL's DB: https://docs.aws.amazon.com/dms/latest/sbs/chap-oracle2postgresql.steps.configurepostgresql.html When I do with postgres user - 1 ALTER USER postgresql_dms_user WITH SUPERUSER; Got postgres=> ALTER USER postgresql_dms_user WITH SUPERUSER; ERROR: must be superuser to alter superusers When I do a grant to sct user, got - 2 postgres=> GRANT ALL ON SEQUENCES IN SCHEMA main TO postgresql_sct_user; ERROR: syntax error at or near "IN" Line 1: GRANT ALL ON SEQUENCES IN SCHEMA main TO postgresql_sct_user... --- About 1, AWS' Aurora PostgreSQL' postgres user isn't the superuser Role name | Group postgres | {rds_superuser} Then how to grant a superuser to a new user? About 2, I'm using PostgreSQL 12 version in the RDS, does the syntax not supported?