tmp session read-only

It’s a /usr/tmpDSK (see OP’s OP) which can become corrupt fairly easily. Best bet is to stop any processes that have files open on /tmp which you can check with:
lsof /tmp

Then umount /tmp and /var/tmp:
umount -l /tmp
umount -l /var/tmp

Then remove the corrupt partition file:
rm -fv /usr/tmpDSK

Then create a nice new one:
/scripts/securetmp

/sbin/shutdown -r now
df -h
cd /tmp
ls
rm -rf sess_*
touch tt
cd ..
service mysql stop
service httpd stop
umount /var/tmp
umount /tmp
rm -rf /usr/tmpDSK
/scripts/securetmp –auto
df -h
service mysql start
service httpd start
cd /tmp
touch tt