Xerox 530 System Management Reference Manual page 28

Table 11. Default Area Allocations
Number of Tracks
Area Default Allocation A
B
C/E
D
SP Only large enough to contain RBM, TVECT, 35 19 37 23
BOOT, and all standard processors (see Table 9).
SD
Only large enough to contain nominally large
17
8 16 10
RBMGO and RBMOV files, and other small
files RBMS2, RBMID, etc.).
- - - - - _ .
Sl Only large enough to contain the Basic
7
4
7
5
FORTRAN IV libraries: Standard precision, ex-
tended precision and common, or main libraries.
--------.-------~
-- --
- .--------
- -
CP Only large enough to contain all of background. t bkg. (words) bkg. (words) bkg. (words) bkg. (words)
2880 6144 3072 5120
------ ----
-------
-.- _._------
~-
BT Remaining disk space up to and including the "All" "All" "All" "All"
last available track.
tlf the ANALYSIS, CP option is selected, the default size of CP wi
II
be large enough to contain all of memory.
explicit specifications following a subsequent device def-
inition. (See "Rule For Placement of System Bootstrap ",
above, concerning SK usage.)
Rule. For Adding Nondefault Areas to the Default Device.
If nondefault areas are to be allocated on the device re-
ceiving the default system-area allocations, at least the
default BT area definition (effectively BT=All, BG) must
be superseded by an explicit specification - not specifying
All - preceding the nondefault area specifi cations. (This
is because the default "BT=All" allocation effectively in-
hibits any further nondefault area specifications for that
device, including SK specifications.)
General Rule For Ordering of Areas. There is no advantage
in any particular arrangement of disk areas on fixed-head
devices (e.g., 720x or 7232). However, the arrangEl-
ment of areas on a movable-arm device (e. g., 724x' or
725x) can significantly affect performance. The general
guideline to be followed in the latter case is to allocate
the di sk areas such that the most frequently used areas
are in the central cylinders (e.g., cylinder 100 for a
724x, equiva lent to track number 2000) and the least fre-
quently used areas are in the outer or inner cylinders. Such
organization increases the probability of small arm motion
when disk I/O is required.
22 Disk Storage Allocation Guidel ines
Allocation Example. The following example of combined
default and explicit allocation will illustrate the various
poi nts made above.
7204/BO,
5
SP:=: 40
BT
=
20
CP
=
0
FP
=
30
UD
=
All, BG
7242/CO
SK
=
20
SO
=,
25
The specifications following the 7204 device definition re-
define the SP area extent, leave the SO and Sl default
allocations unmodified, redefine the BT area, suppress the
CP area, and add the FP and UD areas. The subsequent SO
area specification following the 7242 device definition
effectively "moves" and reallocates the default SD area,
leavi ng the order of areas on the system devi ce (7204) as
SP, S l, BT, FP and UD. Note that the 7242 devi ce will