use SQL LOADER. this is sample


LOAD DATA
CHARACTERSET WE8MSWIN1252
INFILE '/d:\oracle\bin\file_name.txt'
READBUFFERS 4
TRUNCATE
INTO TABLE table_name
REENABLE DISABLED_CONSTRAINTS
FIELDS TERMINATED BY '|'
TRAILING NULLCOLS
( fld_1 INTEGER EXTERNAL
, fld_2 CHAR
, fld_3 CHAR
)