Run this command
TSS WHOHAS ACID(user)
Likely the User owns his own dataset high level qualifier that most likely is permitted to another acid(s).
Issue TSS WHOHAS DSN(user) Then you have a couple of options:
1) If you need to keep the ownership and permits, undercut the ownership to another acid (preferably a department acid), and then delete the acid:
TSS ADD(dept) DSN(user) UNDERCUT
2) If you don't want to keep the ownership and permits, revoke all the permits from the TSS WHOHAS output and then delete the acid.