If you drop the default role for a user, the system no longer defaults to a role when the user logs on, and the user must use the SET ROLE statement to activate a role.
The system records DROP statements in the Data Dictionary. However, a DROP ROLE statement does not affect the user rows in DBC.Dbase, so the system does not reset the corresponding default role setting for affected users. When an affected user next logs on, the system does not return an error or warning if the role does not exist.
You can reset the default role for a user with the MODIFY USER statement.