SQL> connect sys as sysdba
Enter password:
Connected to an idle instance.
SQL> startup
ORA-01012: not logged on
SQL> startup mount;
ORA-01012: not logged on
After some googling and deciding that I do not want to mess with resetting memory sizes, I came across "SHUTDOWN ABORT;" and it fixed all my problems.
SQL> SHUTDOWN ABORT
ORACLE instance shut down.
SQL> STARTUP
ORACLE instance started.
Total System Global Area 631914496 bytes
Fixed Size 1338364 bytes
Variable Size 440402948 bytes
Database Buffers 184549376 bytes
Redo Buffers 5623808 bytes
Database mounted.
Database opened.