You can use a permanent access key and secret key to access the Amazon S3 resources. Anyone with the keys can access sensitive information from the AWS resources. When you use an assume role, it allows existing Identity and Access Management (IAM) users to access the Amazon S3 resources for a limited period, helping you to securely control access to these resources.

You can use the assume role in Amazon S3 V2 Connector to access Amazon S3 resources. In Amazon Redshift V2 Connector, you can use the assume role to access the Amazon S3 staging bucket to stage the Amazon Redshift data before writing to Amazon Redshift.

You can use IAM roles to delegate access to IAM users managed within your account. IAM users under a different AWS account, IAM users under a different AWS account and using an External ID for enhanced security, or for an EC2 role to access an AWS service such as EC2.