6.8 Emulated Tape Devices

Tape device statements are used to define tape devices to the Hercules configuration. Five types of
emulation are supported:

6.8.1 SCSI Tapes

6.8.1.1 Function

When defining SCSI tapes the argument specifies the tape device name (usually /dev/nst0). SCSI tapes
are read and written using variable length EBCDIC blocks and filemarks exactly like a mainframe tape
volume (see also the AUTO_SCSI_MOUNT system parameter).

6.8.1.2 Syntax

Descriptive

[--no-erg] [--blkid---blkid-22]

Diagram

Êʬ¬¬ addr ¬¬¬ ¬¬¬ ¬¬¬§¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬§¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬Ê

--no-

ʬ¬¬§¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬§¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬ÊÍ

--blkid-

--blkid-2

6.8.1.3 Parameter

devaddr

This is the device address.

devtype

This is the device type. Valid device types are 3410, 3420, 3422, 3430, 3480, 3490,
8809 and 9347.

devname

The tape device name (usually “/dev/nst0” on Linux or “\\.\Tape0” on Windows).

--no-erg

This option is intended to prevent issuance of the Erase Gap command to those
SCSI tape drives that do not support it (e.g. Quantum DLT series). It causes Her-

cules's device emulation logic to ignore any ‘Erase Gap’ commands issued to the
drive and to return immediate success instead.

This option should only be used (specified) for drives such as the Quantum which
support switching from read mode to write mode in the middle of a data stream
without the need of an intervening ‘Erase Gap’ command. Specifying it for any
other model SCSI drive may cause incorrect functioning as a result of the Erase
Gap command not being issued to the actual SCSI hardware.

Check the manufacturer information for your particular model of SCSI-attached
tape drive (and/or use Fish's "ftape" Windows utility) to determine whether or not
this option is needed for your particular drive.

--blkid-32

This option indicates that your SCSI-attached tape drive only supports 32-bit block-
ids (as used by 3590 drives) and not the 22-bit format used by 3480/3490 drives.
You should only specify this option if you intend to define the drive as a model 3480
or 3490 device and then only if your actual SCSI drive uses 32-bit block-ids. If you
define your Hercules tape drive as a model 3590 device however this option is not
required as 3590 drives are already presumed to use 32-bit block-ids.

Specifying this option on a 3480/3490 device statement will cause Hercules device
emulation logic to automatically translate the actual SCSI tape drive's 32-bit block-
id into 22-bit format before returning it back to the guest operating system (since
that is the format it expects it to be in for a model 3480/3490 drive), and to translate
the guest's 22-bit format block-id into 32-bit format before sending it to the actual
SCSI hardware (since that is the format that the actual hardware requires it to be
in).

--blkid-22

This is the opposite of the above --blkid-32 option.

6.8.1.4 Examples

Example 1:

Define a 3420 tape device on device address 0580. The tape device is a SCSI-attached tape drive which
only supports 32-bit block-ids.

0580 3420 /dev/nst0 --blkid-32

Example 2:

Define a 3490 tape device on device address 0581. The tape device is a SCSI-attached tape drive which
supports 22-bit block-ids. Ignore any ‘Erase Gap’ commands.

0581 3490 \\.\Tape0 --no-erg --blkid-22