DB Startup Hangs on AIX

OS: AIX 7.1

DB: Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bitNo RAC, No PDB. (Pretty plain-vanilla)

We recently had an datacenter outage that impacted our Oracle AIX environments. After the servers were restarted, I am not able to start Oracle.

I've tried several startup methods. In each case, the startup just hangs.

For instance, using sqlplus /nolog ... connect / as sysdba (or conncect sys as sysdba), it just sits there at

SQL> startup

It then lets me type into the terminal session, but won't let me ctl-c out, and it doesn't respond to anything. (quit, exit, etc.)

System is idle.

The dbstart command $ORACLE_HOME/bin/dbstartsimilarly hangs. It's log file contains SQL> Connected to an idle instance.