HP 3000 Manuals HP 3000 Manuals
Specifying Disk Volume Restrictions
MPE/iX makes a distinction between the device and the media. The device
is the disk drive and the media is the disk pack. The MPE/iX volume
management facility controls the media and divides the media into three
entities:
* Volume set, a set of related disk packs assigned to the group in
which you create your file.
* Volume class, a subset of a volume set. A volume can be assigned
to more than one volume class.
* Volume, a single disk pack. Each volume on a system is a member
of a volume set.
By default, when you create (or otherwise access) a disk file and data is
posted to disk, new extents are placed wherever space is available on any
volume within the volume class DISC assigned to the group in which your
file resides.
You can use either the volume name option or the volume class option of
HPFOPEN, or the device parameter of FOPEN, to specify either a volume
name or a volume class name, thus restricting the placement of your
file's extents to either the specified volume or to the specified volume
class within the volume set.
The device parameter of FOPEN also allows you to specify a volume name or
a volume class in an additional manner, due to the necessity of
maintaining FOPEN compatibility with MPE V/E based computer systems. If
an LDEV (a logical device number used to identify a device) is passed
into FOPEN, MPE/iX translates the LDEV into the volume name that is
currently mounted on the disk device and places the volume name in the
file's label. Similarly, a device class that is associated to a disk
device is translated into the volume class name.
NOTE HPFOPEN fails if, when creating a disk file, an LDEV is passed to
volume name option for a mounted disk or a device class is passed
to volume class option.