Split Large File

HI,

i've to split a large file which inputs seems like :

Input file name_file.txt
00001|AAAA|MAIL|DATEOFBIRTHT|.......
00001|AAAA|MAIL|DATEOFBIRTHT|.......
00002|BBBB|MAIL|DATEOFBIRTHT|.......
00002|BBBB|MAIL|DATEOFBIRTHT|.......
00003|CCCC|MAIL|DATEOFBIRTHT|.......
00004|DDDD|MAIL|DATEOFBIRTHT|.......
00005|EEEE|MAIL|DATEOFBIRTHT|.......
00006|FFFF|MAIL|DATEOFBIRTHT|.......
00007|MMMM|MAIL|DATEOFBIRTHT|.......
00008|TTTT|MAIL|DATEOFBIRTHT|.......
00008|TTTT|MAIL|DATEOFBIRTHT|.......
00009|HHHH|MAIL|DATEOFBIRTHT|.......
00010|KKKK|MAIL|DATEOFBIRTHT|.......

IF I WANT TO SPLIT EVERY 5 LINES BASED ON THE FIRST AND SECOND COMUMNS FOR EXAMPLE I MUST HAVE:

out1.txt
00001|AAAA|MAIL|DATEOFBIRTHT|.......
00001|AAAA|MAIL|DATEOFBIRTHT|.......
00002|BBBB|MAIL|DATEOFBIRTHT|.......
00002|BBBB|MAIL|DATEOFBIRTHT|.......
00003|CCCC|MAIL|DATEOFBIRTHT|.......
00004|DDDD|MAIL|DATEOFBIRTHT|.......
00005|EEEE|MAIL|DATEOFBIRTHT|.......
out2.txt
00006|FFFF|MAIL|DATEOFBIRTHT|.......
00007|MMMM|MAIL|DATEOFBIRTHT|.......
00008|TTTT|MAIL|DATEOFBIRTHT|.......
00008|TTTT|MAIL|DATEOFBIRTHT|.......
00009|HHHH|MAIL|DATEOFBIRTHT|.......
00010|KKKK|MAIL|DATEOFBIRTHT|.......

if i have two lines with the same value in the first and second column i will count them as one line.
plesz help

awk -F'|' '{a[$1FS$2]++;f="out"n+1".txt"}a[$1FS$2]==1{b++}{print > f}b==c{n++;b=0;close(f)}' c=5  big_file

Where c=5 is your lines counter. Or with less typing :

awk -F'|' '!a[$1FS$2]++{b++}{print > (f="out"n+1".txt")}b==c{n++;b=0;close(f)}' c=5  big_file