Management has decided that the database must be available 24 hours a day， 7 days a week. Given this requirement， which type of backup is required？（）

A.Directory server
B.Hostname adaptor
C.TCP/IP host file
D.Connection Manager
E.connecting pooling
F.external procedures
G.listener names and protocol addresses
H.Net Service names in a tnsnames.ora file
I.naming methods the client uses to resolve connect identifiers

A.data files
B.control file
C.password file
D.online redo log files
E.initialization parameter file