Everything goes fine with my Oracle 11G but out of the sudden it give me this error. ORA-12560: TNS:protocol adapter error.
I then look at the Event Viewer logs and give me another error message.
ACTION : ‘CONNECT’ DATABASE USER: ‘/’ PRIVILEGE : SYSDBA CLIENT USER: NT AUTHORITY\SYSTEM CLIENT TERMINAL: MYAREJAE STATUS: 0 .
Googling around give me below solution. Just run the command and everything goes back to normal.
oradim -edit -sid orcl -startmode auto
Depending on the situation, I think maybe this solution is not necessary true for everyone but at least it works for me.