Cause of ORA-1089 error

I'm getting the ORA-01089 error and the system is allowing me to connect to the database as sysdba using SQL*Plus. I must say that I'm novice when it comes to Oracle. Any suggestions?
The ORA-1089 error is telling you that someone attempted to perform a SHUTDOWN of the database. No new transactions can be started. If this condition persists for a long period of time, sign on to the database as SYSDBA and issue the following:

SHUTDOWN ABORT
STARTUP

This will force the database to shut down immediately and then start it back up. Transactions can now take place.