OS: Sun Solaris
Allpication: Oracle 7.3.4
I'm running Oracle in archivelog mode which means that Oracle's log files containing roll forward data are automatically archived as they are filled up. I underestimated the expected amount of archived log data required for the new application. As a result, the file system containing archives became 100% full.
When this happened I had 30 recently created archive files. Their names and sizes were listed by ls -l. df -k showed 100%.
I deleted some old files and got this file system down to about 90%. Then we had to reboot the machine (for a different reason). When it came up... all 30 Oracle archive log files were gone! df -k showed much more free space. I'm sure noone deleted them.