The mdbadmin (for AutoSys 11.0) database user is only used during the installation of the product and/or during the applying of patches. The id is used as the schema owner for the AutoSys database objects.
Its password is NOT stored in any AutoSys configuration file or database table. You can use the native database commands or utilities to change its password.
To change the "autosys" database user's password, one should use autosys_secure, as in past AutoSys versions.
This will ensure the password is changed in all the proper locations.
Proper locations being: In the database system security tables, in the AutoSys database tables and in our configuration file $AUTOUSER/config.$AUTOSERV on unix or in the registry for Windows machines.