Hello, we recently upgraded from AIX 5.2.9 to 5.3.6 and in the process the wtmp file was cleared out. Before the upgrade the system had not been rebooted in a very long time, so i'm curious if the clearing of the file is related to the upgrade or the reboot? If it was related to the reboot is there a way to set AIX so the file is not cleared after each reboot?
During a normal reboot the wtmp file is not cleared, so perhaps it was due to the upgrade or some other effect (deleted somehow by a process started from inittab, a process in the k-scripts in /etc/rc.d of runlevel 2 or something such).
bakunin
How did you upgrade? Assumably you did not use "New and Complete Overwrite" (cause in that case you might have guessed already why wtmp dissappeared). So Migration Installation and Preservation Installation are left ... If you did a Preservation Installation you fell into the "IBM-Speak" trap 
as such an installation will wipe out the whole system configuration including /var. You could spare some files from being overwritten by including them into the /etc/preserve.list (/etc/filesystems is kept as a default) but the rest ... well 