I can't repeat this. Here is what I get.
yottadb>Set tempfile="/tmp/1.txt",file="/tmp/2.txt"
yottadb>Open tempfile Use tempfile Write "1" Close tempfile
yottadb>
NOTE: At this point I verify that 1.txt in /tmp/1.txt contains "1"
yottadb>OOpen file Use file Write "2" Close file
NOTE: at this point 1.txt contains '1' and 2.txt contains '2'
yottadb>Open tempfile
NOTE: no change in text files, both still OK
yottadb>Close tempfile:(replace=file)
%YDB-E-DEVPARUNK, Deviceparameter unknown
yottadb>
NOTE: no change in text files, both still OK
yottadb>w $ZVER
GT.M V6.3-008 Linux x86_64
yottadb>