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6.8.4.3 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.

hetfile

The filename (and path) of the HET file or “*”. An asterisk defines an empty tape
station. The tape must be manually loaded on request.

If the filename starts with the “@” character (at sign), the file then describes a list of
tape emulation files to be loaded in succession. The syntax of each line in this file is
identical to the information that can be coded directly after the device type in the
overall configuration file. Any emulation file name parameter specified in this file
may be substituted by the character “*”, in which case it specifies a set of options to
be applied to all additional emulation files specified in the list.

This function emulates an Automatic Cartridge Feeder (ACF). The ACF is a feature
on cartridge type tape drives (3480, 3490, etc.) that automatically loads a new tape
when a tape is removed from the drive. There is no real control over this device by
the host as it just keeps on feeding tapes one after the other. Although the ACF
feature is unique to cartridge type systems, the emulation accepts the use of the
same technique for emulated 1/2 inch tapes reel drives as well.

Parameters are appended in succession. In all cases, if the same parameter is
coded more than once, the last instance takes precedence. Therefore it is possible
to specify a set of parameters in the base configuration file, another on an “*” line
and another for each individual line in the list of files. Parameters are then appen-
ded in that order. A SCSI tape device should not be given in a file list!

AWSTAPE

The AWSTAPE argument causes HET files to be written in AWSTAPE format. This
disables the additional feature provided by the HET format.

IDRC=

COMPRESS and IDRC control whether compression should be used when writing
to HET files. The value of n can be “1” to turn compression on (the default), or can
be “0” to turn compression off. IDRC is currently a synonym for COMPRESS but
may be used in the future to control another emulated tape drive feature. Therefore
COMPRESS is the preferred method to turn compression on or off.

COMPRESS=

This is the same as IDRC=.

METHOD=

The METHOD argument allows you to specify which compression method to use. A

value of “1” forces the use of ZLIB compression. A value of “2” forces the use of
BZIP2 compression. The default is “1”.

LEVEL=

The LEVEL option controls the level of compression. It ranges from “1” (for fastest
compression) to “9” (for best compression). The default compression level is “4”.

CHUNKSIZE=

The CHUNKSIZE option allows you to create HET files with different chunk sizes.
The AWSTAPE (and therefore HET) formats allow each tape block to be logically
broken up into smaller chunks. For instance, if the S/3x0 application creates tapes
with a block size of 27998, those blocks would be broken down into nnnnn sized
chunks. Although possible it is not recommended to change the chunk size, as de-
creasing this may reduce compression performance. The range of nnnnn is from
4096 to 65535. 65535 is the default.

STRICTSIZE=

Upon reaching the tape file size limit, depending on strictsize, the tape file will or
will not be truncated to enforce the maxsize limit. The limit is only enforced during a
write type operation. If the file already exists and the program only reads the file,
then the file will not be truncated, regardless of the strictsize setting.

This affects any write that starts below the limit, but that would extend beyond the
limit. The strictsize parameter only affects compressed HET files. On AWS tapes,
the limit is always enforced, but the file is not truncated (the write does not occur,
because first AWS tapes are never truncated and second the effects of the write
are known in advance).

Regardless of strictsize, any write operation (Write, Write TM) will return a Unit
Check with Equipment Check to the program if the file size exceeds the predefined
limit. If strictsize is “0”, the write will actually have been performed on the tape file.
When strictsize is set to “1”, the file will be truncated on the preceding tape block
boundary.

Care must be taken that regardless of the strictsize setting, the tape may become
unusable for the guest program should such an event occur (absence of a Tape
Mark for example). This option has no effect if maxsize is 0. The default is “0” (do
not truncate).

The remaining parameters are described in section

6.8.4.4 Examples

Example 1:

Define a 3490 tape device on device address 0580. The tape device is a HET virtual file with name
"R0674A.HET" located in path "/S390/TAPES/". BZIP2 compression has to be turned on at a level of 9
(best compression).

0580 3490 /S390/TAPES/R0674A.HET COMPRESS=1 METHOD=2 LEVEL=9

Example 2:

Define a 3490 tape device on device address 0580. The tape device is a HET virtual file with name
"R0675A.HET" located in path "/S390/TAPES/". Mount the tape as read/write.

0580 3490 /S390/TAPES/R0675A.HET RING