The AS Clause

Without the AS clause, the user who executes the REVOKE statement must be a grantor of the privilege that is being revoked. The DBA or the owner of the fragment can use the AS clause to specify another user (who must be the grantor of the privilege) as the revoker of privileges on a fragment.

The AS clause provides the only mechanism by which privileges can be revoked on a fragment whose owner is an authorization identifier that is not a valid user account known to the operating system.