OCP 1Z0 053 174

174.What Oracle process runs when the database is in ARCHIVELOG mode but not when it is in 
NOARCHIVELOG mode? 
A. MMON 
B. LGWR 
C. ARCH 
D. ARWR 
E. COPY 
Answer: C

http://docs.oracle.com/cd/E11882_01/server.112/e40540/process.htm#CNCPT1257

Archiver Processes (ARCn)

The archiver processes (ARCn) copy online redo log files to offline storage after a redo log switch occurs. These processes can also collect transaction redo data and transmit it to standby database destinations. ARCn processes exist only when the database is in ARCHIVELOG mode and automatic archiving is enabled.