Accroding to the DP 8 support matrix:
http://support.openview.hp.com/selfsolve/document/KM00453104
OEL 5.9 is NOT supported as a Cell Manager or an Installation Server for DP 8 pg 1
Oracle Enterprise Linux (OEL) 6.4, 6.5 (64-bit) (x64)
It is supported as a Disk Agent and a Media agent pg 2,3
Linux (32-bit): Red Hat Enterprise Linux (RHEL) - 5.x, 6.0, 6.1, 6.2, 6.3
SUSE Linux Enterprise Server (SLES) 9, 10, 11
Oracle Enterprise Linux, 5.x, 6.0, 6.1, 6.2, 6.3
CentOS 5.x, 6.0, 6.1, 6.2, 6.3