Hi,
I don't think there exists some kind of checksum of table/file. What operating system do you use on mainframe: zOS, VSE, VM or zLinux? What version of DB2 are you using and fixpack level? Please tell us more about you system.
What would you like to do with extracted flat files? Will you move them to some DB2 on Linux/Unix/Windows? What is the purpose of extracted flat files?