DBUA0 Instance during 11g Upgrade

Recently when upgrading to 11g Release 1 , I found an unknown instance DBUA0 running on the server. I could not connect to the DBUA0 Instance to check further.

oudbtst 24771 1 0 15:16 ? 00:00:00 ora_pmon_DBUA0
oudbtst 24773 1 0 15:16 ? 00:00:00 ora_vktm_DBUA0
oudbtst 24777 1 0 15:16 ? 00:00:00 ora_diag_DBUA0
oudbtst 24779 1 0 15:16 ? 00:00:00 ora_dbrm_DBUA0
oudbtst 24781 1 0 15:16 ? 00:00:00 ora_psp0_DBUA0
oudbtst 24783 1 0 15:16 ? 00:00:00 ora_dia0_DBUA0
oudbtst 24785 1 0 15:16 ? 00:00:00 ora_mman_DBUA0
oudbtst 24787 1 0 15:16 ? 00:00:00 ora_dbw0_DBUA0
oudbtst 24789 1 0 15:16 ? 00:00:00 ora_lgwr_DBUA0
oudbtst 24791 1 0 15:16 ? 00:00:00 ora_ckpt_DBUA0
oudbtst 24793 1 0 15:16 ? 00:00:00 ora_smon_DBUA0
oudbtst 24795 1 0 15:16 ? 00:00:00 ora_reco_DBUA0

Raised a ticket with Oracle Support and found that DBUA0 is an Instance created by DBUA when upgrading the database and the presence of the DBUA0 process does not indicate a problem with the upgrade or that any action is required.

DBUA shuts down the instance after the upgrade is completed but for some reasons it did not.

So I had to reboot the server to make sure every thing with the upgrade is fine.