CellServer Backup error: ACLs Read only filesystem problem

Dear all,
I'm quite a newbie for Hp-UX, anyway I set up a brand new HP-UX 11.31 rx3600 machine to act as backup server. It has Dataprotector 6.0 and (for now, sinc ethe machine is still under test and customization) a little HP Autoloader 1/8 LTO2 SCSI device.
The pathes installed (and applied to the Cell Server itself) are:
FOR DP 6.0:
PHSS_36610 1.0 OV DP6.00 IA-64 patch - EMC packet
PHSS_37148 1.0 OV DP6.00 IA-64 patch - ORACLE8 packet
PHSS_37163 1.0 OV DP6.00 IA-64 patch - SMISA packet
PHSS_37165 1.0 OV DP6.00 IA-64 patch - INFORMIX packet
PHSS_37167 1.0 OV DP6.00 IA-64 patch - DB2 packet
PHSS_37300 1.0 OV DP6.00 IA-64 patch - DOC packet
PHSS_37571 1.0 OV DP6.00 IA-64 patch - SSEA packet
PHSS_37746 1.0 OV DP6.00 IA-64 patch - SAP packet
PHSS_37750 1.0 OV DP6.00 IA-64 patch - SAPDB packet
PHSS_37817 1.0 OV DP6.00 IA-64 patch - CORE packet
PHSS_37819 1.0 OV DP6.00 IA-64 patch - CC packet
PHSS_37821 1.0 OV DP6.00 IA-64 patch - CS packet
PHSS_37882 1.0 OV DP6.00 IA-64 patch - DA packet
PHSS_38122 1.0 OV DP6.00 IA-64 patch - MA packet
PHSS_38230 1.0 OV DP6.00 IA-64 patch - LOTUS packet

FOR HP-UX:
BUNDLE B.2008.06.09 Patch Bundle
FEATURE11i B.11.31.0803.318b Feature Enablement Patches for HP-UX 11i v3, March 2008
HWEnable11i B.11.31.0803.318a Hardware Enablement Patches for HP-UX 11i v3, March 2008
QPKAPPS B.11.31.0803.318a Applications Patches for HP-UX 11i v3, March 2008

So practically it's updated to the latest patches available on 12-June-2008.

I'm trying to setup some test backup on cellserver itself, and I created a specification that does the full backup of entire cellserver filesystems, plus the internal DP idb database backup.
When the backup is near to its end I get this error:
[Minor] From: VBDA@itmilif1.eur.cchbc.com "itmilif1.eur.cchbc.com [/]" Time: 14/06/2008 14.03.53
[81:84] /dev/deviceFileSystem
Cannot read ACLs: ([30] Read-only file system).

Is this ok? Can I avoid this?
Ok, since I have "make-tape-recovery" full backup of OS I can avoid to backup it with DP, but I want to better understand what's that error, why I get it, if it's a correct behaviour or not and, finally, if it's better to keep that error (or avoid to backup / filesystem), or change the setting which cause the error itself (maybe putting / in read/write).

Many thanks, Alessandro