Recording Mode - Control Data Corporation 3300 Reference Manual

3.S.10
RECORDING MODE
3-34
The RECORDING MODE clause of a file description entry specifies the
manner in which data is recorded on external storage devices.
jl
BINARY I
RECORDING DECIMAL
MODElS lSECTORI
TRACK
[{
LOW }
HIGH
. HYPER
[ 1
SEGMENTED
~]
CONTIGUOUS \
DE NffiTY ]
I
For magnetic tape, the density settings are: LOW=200 bpi, HIGH=556 bpi,
and HYPER=800 bpi. If this clause is not present, a RECORDING MODE of
DECIMAL HIGH DENSITY will be assumed.
The SECTOR/TRACK and SEGMENTED/CONTIGUOUS options apply only to
mass storage files. When the FILE-LIMITS clause of the Environment
Division is specified, the input-output control system will internally allocate
and/or expand permanent mass storage files at object time. This allocation
is performed according to the RECORDING MODE specification. SECTOR
indicates that the minimum unit of allocation is a sector; TRACK that it is a
track. SEGMENTED means that the file may be located in different areas of
the same disk file. The MASTER file supervisor keeps track automatically
of the locations of file portions. If CONTIGUOUS is specified, the file is
assigned to one area large enough to hold the entire file on a single device
(disk file or disk pack). The input-output control system automatically
releases any unused portion of any file specified as SECTOR SEGMENTED.
If RECORDING MODE is not specified for mass storage files, SECTOR
SEGMENTED is assumed. Whenever possible, mass storage files should
be allocated in CONTIGUOUS mode to minimize read/write head movement,
thus increasing the rate of proceSSing.
A file assigned to TTY or CRT is always assumed to have a recording mode
of DECIMAL.
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