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4. SYSTEM GENERATION
INTRODUCTION
System generation (SYSG E N) is a process that produces an
RBM system IItai lored
ll
to the specific needs of a particular
installation. The primary object ofthe process is to achieve
the least system overhead cost consistent with functional
requirements, in terms of memory and system disk space and
of criti cal response times.
The selection criteria for in-
cluding or excluding optional RBM functions, for deter-
mining the size of various system tables and areas, etc.,
are described in Chapter 3. The functional and operational
aspects of the SYSGEN process are described in the pre-
sent chapter.
SYSGEN FUNCTIONAL OVERVIEW
System generation is performed by a stand-alone SYSGE N
program.
The process essentially involves the selection
and consolidation of Xerox-supplied RBM modules, based
on user input parameters, and is performed in two phases:
1.
A definition phase - or phase 1, which collects user
supplied parameters that
•
•
•
Describe the hardware configuration.
Select the optional software features and functions.
Determine various table sizes, memory partition
boundaries, and system disk area exte~ts.
Based on this information, the definition phase gen-
erates a core image of resident RBM consisting of the
mandatory resident modules, optional resident modules,
the RBM overlay area, and various I/O and other sys-
tem tables.
(The tables are compacted as far as
possible into otherwise unutilized low-core spaces.)
The resident RBM modules are supplied in relocatable
form.
Phase 1 also generates several tables - memory
and disk allocations, monitor symbol values, etc. -
for later use by phase 2 and subsequently by the newly
generated operating system itself.
(Certain of these
tables are completed by phase 2 processing. )
2.
A system load (SYSLOAD) phase - or phase 2, which
generates on disk the nonresident portion of RBM and
completes the system disk image of the entire Monitor
(resident and nonresident), using information supplied
by phase 1.
In so doing, it
•
Completes the disk allocation determined by
phase 1.
•
Absolutizes and loads onto the system disk the re-
quired RBM overlays (mandatory and optionally
selected nonresident modules), which are supplied
in relocatable form.
24
System Generation
•
Completes the RBM over! ay loading control table.
•
Completes the resident monitor core image and
loads it onto the system disk.
•
Completes the system disk (insofar as the Monitor
is concerned) by adding such items as the RBM
bootstrap, Transfer Vector Table, and Symbol
Table files, and initializing the SP and SD area
file directories.
Note that, at the user's option, certain of the normally
nonresident modules may be loaded by phase 2 as
resident routines rather than as overlays - the normal
case. This option is controlled by phase-l parameters.
Throughout, both phase 1 and phase 2 test for various error
conditions such as invalid parameters, loading errors, disk
area overflow, excessive module size, and invalid load
items.
OPERATIONAL OVERVIEW
The SYSGEN process is initiated by a hardware load from
either a magnetic tape unit, paper tape reader, or card
reader, depending upon which form of system-release media
is employed.
In any case, the SYSGEN program is self-
loading.
The system release tape or deck is self-sufficient
in that
it
contains all of the materials required for genera-
tion of RBM.
(The format of the system release tape/deck
is described below. )
Once SYSGE N is loaded, the user is requested to supply,
via the operator's console, the model number and device
number of the input device through which all further user
inputs - parameters, options, etc. - wi
II
be suppl ied,
and of the output device (if any) on which input requests
are to be printed and user responses logged.
If the con-
sole (keyboard/printer) is chosen for these subsequent inputs
and outputs, the definition-phase operational sequence is
controlled from this point on by further printed messages -
requests for key-ins - from the SYSGEN program.
User input need not be via the keyboard/printer; a paper
tape reader or card reader may be utilized. In this case, the
individual option and parameter records must be ordered in
exactly the same sequence as they would be entered in re-
sponse to prompts at the keyboard/printer. The end of the
definition phase is signaled by the message LOAD RESIDENT
MODULES, at which point the required resident RBM rou-
tines are read from the file of resident modules (see
II
System-
Release Tape Format", below).
The beginning of the SYSLOAD phase (phase 2) is marked
by the message RBM SYSLOAD followed by the request
INPUT OPTION (ALL, UPD, or PA).
The ALL option is
used for an initial system generation, or whenever all areas
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