Create Delta File in JCL

I need to create delta file for a daily feed please let me know how to do it. even if there is a single character change in new file the new record should replace the old one. consider first 5 characters as a key parameter
example:
file-1
12345 abc dat1
12346 def dat2
12347 5ab ddd4
file-2
12345 abc dat1 --> same in both so no need of this record
12346 bbb dat2 --> minor changes in file-2 so it should be in output
13345 2gh dat3 --> record not at all present so this will be added to o/p
output:
12346 bbb dat2
13345 2gh dat3