Technical data

Managing Storage Media
9.1 Understanding Storage Media Concepts
Refer to the OpenVMS System Management Utilities Reference Manual for details
about using the /DENSITY qualifier with these utilities. Also refer to Chapter 11
for details about using the /DENSITY qualifier with BACKUP.
Example
$ INITIALIZE/DENSITY=tk85 MKA500: TEST
The command in this example initializes the media in the MKA500: drive to tk85
density with a label of TEST.
Densities Supported
The following densities are valid in the command strings for DCL commands and
system management utilities: 800, 1600, 6250, DAT, 833, DDS1, DDS2, DDS3,
DDS4, TK50, TK70, TK85, TK86, TK87, TK88, TK89, 8200, 8500, 3480, 3490E,
AIC, AIT, and DEFAULT.
Usage Notes
You cannot use multiple tape densities on one piece of media. In other words, one
density applies to one piece of media. If you do not specify a density, the default
density is used; the default is the highest density a particular drive supports.
Density changes can occur only at beginning-of-tape (BOT). Once media is
initialized to a density, the media remains at that density until it is reinitialized
to a different density.
If a density is not supported on a particular device, depending on the drive, the
density field either remains the same or takes the default. If a drive does not
support the density you select, the system displays an invalid density error. Some
drives do not report the error and simply ignore your selection, leaving the media
at the previous density.
When media is set to a specific density, the ‘‘density’’ field displayed when you
enter
$ SHOW DEVICE/FULL MKA300: , for example, displays the corresponding ASCII
string for density.
Magtape JENSO3$MKA300:, device type TZ87, is online, file-oriented device, error
logging is enabled, controller supports compaction (compaction, disabled),
device supports fastskip.
Error count 0 Operations completed 0
Owner process "" Owner UIC [SYSTEM]
Owner process ID 00000000 Dev Prot S:RWPL,O:RWPL,G:R,W
Reference count 0 Default buffer size 2048
Density TK85 Format Normal-11
Volume status: no-unload on dismount, position lost, odd parity.
9.1.4 Public and Private Disk Volumes
A volume is one or more units of storage media that you can mount on a device.
The volume is the largest logical unit of disk file structure.
This section explains the concepts of public and private volumes.
Managing Storage Media 9–13