It's possible to log into the Data Center Security's Unified Management Console (UMC) with a UPN user just fine, but NOT in the DCS Java Console, why not?
DCS 6.9.3 and earlier
The DCS Java console and the UMC console are two different code bases. While both consoles allow you to integrate with Active Directory, and the UMC console allows a DCS Admin to log into it using a UPN user without issue, this option isn't available in the DCS Java console version 6.9.3 and older at this time. Nor is it feasible to fix as it would require a redesign of the Java console.
We are aware of this limitation in DCS version 6.9.3 and earlier and have fixed this issue in DCS version 6.10. To access this capability please upgrade.
For more information involving the upgrade to DCS version 6.10, see this link: Upgrading to Data Center Security: Server Advanced 6.10.
CRE-20928