Oracle Instance/Process stuck - will not shutdown

AIXOracle 11.1.0.7

  Have a DB/Instance that is stuck will not shutdown, but is not truly running.

I see MMON,MMNL,SMON,PSP0,LGWR,DBW0,MMAN,PMON,DIA0,DBRM,VKTM,DIAG,GEN0,and CKPT process in AIX

ps -ef|grep SID

  However, if logon to SQLPLUS on server and try to shutdown immediate or abort will not shut down. 

ORA-01034: ORACLE not available

ORA-27101: shared memory realm does not exist

IBM AIX RISC System/6000 Error: 2: No such file or directory

At first, DBUA would not see it (trying to upgrade it to 11.2.0.3) - message DB is not mounted.

Tried STARTUP/SHUTDOWN, but would never see it.  Sounds like something is stuck.