I was making text file copies of some system utility output (e.g. ioscan) and happened to look at /etc/fstab and found this:
/dev/vg02/lvol1 /prodbkup vxfs ioerror=mwdisable,log,nodatainlog,dev=40
020001 0 0

my other entries look like this:
/dev/vg04/lvol1 /trainbkup vxfs log,nodatainlog 0 0
---
I have no idea why this filesystem is different. tje ioerror=mwdisable and the dev=40020001
What does it mean and does it make sense?

See man mount_vxfs for a description of the ioerror= mount option.

The dev= option seems to be undocumented (at least on the systems I'm looking at). What operating system and version of Veritas Filesystem are you using?

HP-UX B.11.23 U i64

no idea about the Veritas - if you tell me how to find out I will report back

I don't know what dev option means, either, but in general, if you want to read up on Veritas File System (which is what you have), go here: Storage Foundation and High Availability 4.1

I have no clue how to check vxfs version on HPUX, on Solaris or Linux you would check the package/rpm info, whatever package mgmt is used on HPUX should give you the info.

swlist VRTSvxfs will tell you what version you're using.

I think I know what's going on here. If you run the mount -p command to display the mounted filesystems in fstab format, you will probably see a dev= option for every device. I suspect another admin has simply copied and pasted those mount options into fstab at some point; but I imagine the dev= option is meaningless in there as it would be dynamically set to the device number of the device that is mounted.

In other words, don't put it in /etc/fstab.