6.11 CKD DASD De
vices
6.11.1 Function
This device statement is used to define a CKD DASD device to the Hercules configuration. The argument
specifies the name of a file that contains the CKD DASD image or the INET address of a Hercules shared
device server.
The file consists of a 512-byte device header record followed by fixed length track images. The length of
each track image depends on the emulated device type and is always rounded up to the next multiple of
512 bytes.
Volumes larger than 2 GB (for example the 3390, model 3) can be supported by spreading the data
across more than one file. Each file contains a whole number of cylinders. The first file (which contains
cylinders 0-2518 in the case of a 3390) usually has “_1” as the last two characters of its name. The
ckddasd driver allocates the remaining files by replacing the last characters of the file name by the
characters “_2”, “_3” and so on.
If your operating system supports large file sizes (or 64-bit offsets) then volumes larger than 2GB can be
kept in a single file. The two character suffix is not used in this case.
Alternatively the argument may specify the name of a file containg a compressed CKD DASD image
(CCKD DASD files). The CKD driver will automatically detect whether the file contains a regular CKD
image or a compressed CKD image.
6.11.2 Syntax
Descriptive
filename [sfshadowfile
type]
or
ipname [ ] [
] n]
Diagram
Êʬ¬¬ ¬¬¬ ¬¬¬ filename ¬¬¬§¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬§¬¬¬¬¬¬¬¬¬¬¬¬¬Ê
shadowfile
ʬ¬¬§¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬§¬¬¬§¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬§¬¬¬§¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬§¬¬¬¬¬¬¬¬¬¬¬¬¬Ê
ʬ¬¬§¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬§¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬ÊÍ
type