Can I use external compression tools like WinZip, 7zip or winrar to compress rman backup files?
The DBMS is Oracle. A senior DBA claims that backups could be damaged by external compression tools. He argues that the tools shrink blocks which are not full and at a restore the database might have problems because control sums don’t match. I didn't find a source on that.
rman
then you should indeed not touch the files. But rman can do compression on its own (but requires enterprise edition if I'm not mistaken)