Usernames longer than 8 characters cannot be used for MSS. This includes using them to start an enterprise server. As a consequence, if an MF Directory Server administrator signs on with a username that is longer than 8 characters, he or she will have to supply a different username when starting an enterprise server from the Enterprise Server Administration screens.
This restriction also applies to JES and JCL support. Any name referenced in JCL must be uppercase (e.g. USER=XXX), as you cannot use a lowercase or mixed-case username in JCL. You can however use a user with a lower- or mixed-case name to submit jobs.