autochanger.7 (2010 09)

a
autochanger(7) autochanger(7)
NAME
autochanger: schgr, eschgr - SCSI interfaces for medium changer device
DESCRIPTION
An autochanger is a SCSI mass storage device, consisting of a mechanical changer device, one or more
data transfer devices (such as optical disk drives), and media (such as optical disks) for data storage. The
mechanical changer moves media between storage and usage locations within the autochanger.
Two medium changer drivers (
schgr or eschgr) provide access to the medium changer device; eschgr
is the current preferred method of access and
schgr is provided for legacy compatibility. The mechani-
cal changer device can be accessed via these drivers directly to move media within the autochanger.
The
schgr and eschgr medium changer device drivers follow the SCSI specification for medium
changer devices to provide a generic medium changer interface, making it feasible to construct an appli-
cation level driver for any mechanical changer, jukebox, library, or autochanger device (MO, tape, CD-
ROM).
Device Naming Convention
The device naming convention for the autochanger driver enables accessing the changer device.
Legacy character device file names reside in
/dev/rac. Within this directory, names are derived from
the
c#t#d# device naming convention (explained in intro (7)). Unique legacy device names are deter-
mined by the card instance, target address of the SCSI changer device and LUN of the SCSI changer dev-
ice.
Persistent device file names have the form
/dev/rchgr/autochx for character devices. The card
instance, target address and LUN are no longer encoded in the persistent device file name itself (see
intro(7)).
Major and Minor Number Descriptions
The following shows the bit assignments (
dev_t format) used by the schgr changer driver to access the
changer device using legacy device files:
0-7 8-15 16-19 20-22
MAJOR INSTANCE TARGET LUN
MAJOR is the major number of the appropriate driver, INSTANCE is the card instance of the SCSI inter-
face to which the changer device is attached, TARGET is the SCSI target address of the changer device,
LUN is the SCSI LUN of the changer device.
All fields in the device number are specified in hexadecimal notation. Note that there is no support for
hard partitions (sections) in this minor number. If desired, partitioning can be achieved via LVM soft-
partitioning schemes.
Note: The major numbers used by the changer drivers are dynamically assigned starting with release
HP-UX 11i v3.
Following is a long listing showing the major and minor numbers associated with the device special file
name of the changer:
schgr:
crw-rw-rw- 1 root sys 231 0x015000 Apr 22 10:22 /dev/rac/c1t5d0
SCSI MEDIUM CHANGER DEVICE DRIVER
The SCSI medium changer device driver performs moves between different media locations within an
autochanger. Each potential media location has a specific element address and is one of the following ele-
ment types:
storage A location to hold a unit of media not currently in use. Typically most media
will be located in this type of element.
import/export A location for inserting and removing media from the device. Movement of a
unit of media to this type of location is in effect an eject operation. Movement
of a unit of media from this type of location is a load operation.
data transfer A location for accessing media data. This is generally the location of a device
that reads and/or writes data on the media being handled by the media
changer device. Movement to this type of location is a physical-media-mount
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1