[comp.os.vms] DEC Checksums - Non-Unique!!

"Thomas_W._Taylor.WBST147"@XEROX.COM (09/17/87)

We have been using the CHECKSUM program supplied with VMS to determine
if on-disk-created save sets which are then copied to tape for software
distribution are accurate copies.  We copy the savesets from disk to
tape and then use CHECKSUM to verify the taped data.  Because of the
volume of data we do not have the luxury of doing a BACKUP/VERIFY to the
tape.  A copy to the tape with read and/or write check set is an
horrendous consumer of time and system resources.  This seems to work
fine for us, but I have noticed that there are several of the save sets
(rather large files, 8192 byte blocks) have the same checksum.  I could
understand a few instances of this occurring when you have all those
XORs, but I think there are far too many.  Is CHECKSUM finding some
errors which it is not otherswise reporting?  Is there some
characteristic of the save set which makes this situation more likely?
Has anyone seen this before?  Your responses would be appreciated.

			Thomas W. Taylor
			Xerox Corp - 0147
			Webster, NY		14580