HP-UX 10.00 or later creates HFS filesystems with long file names (up to
255 characters) enabled by default, and all VxFS filesystems support long
file names.

To change pre-10.0 HFS filesystems to support long filenames, run
the /etc/convertfs program (see convertfs(1M)).  Note that will NOT be
able to switch back.

Here's how to check if an existing HFS filesystem has long filenames
enabled:

# tunefs -v /dev/rdsk/XXX | grep magic
magic   95014   clean   FS_OK   time    Tue Mar 23 14:13:01 1993
           \__ if = 95014 then long filenames
            \__ if = 11954 then short filenames

You can also look at this on a per directory basis with the POSIX
command getconf:

  $ getconf NAME_MAX directory

where 'directory' is the path to the directory.