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.
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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. |
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