A checksum is a value used to verify the integrity of a file or a data. Checksums are typically used to compare two sets of data to make sure they are the same. If the checksums don't match those of the original file or data, the data may have been altered.
Informatica provides the function MD5() for Checksum generation. This function returns a unique 32-character string of hexadecimal digits 0-9 and a-f.
Syntax : MD5( value ) Return : Unique 32-character string of hexadecimal digits 0-9 and a-f.
Checksum used to cretae unique columns in table when you implement checksum on any field in table during load time then it will automatically find the max value of the field and add 1 for every next record inserted. Basically used in SCD to create Index.