Minimized system footprint

The SCO Embedded Configuration Toolkit is designed to produce SCO UNIX operating environments that work efficiently and effectively within strictly limited RAM resources. An absolute minimum of 4MB of RAM is recommended for all systems (except client controllers and embedded servers). Any available RAM over and above the amount used by the UNIX kernel and filesystem can be used by applications.

A number of limitations are imposed on the runtime environment to maintain this resource limitation, particularly in the number of concurrently running processes and in device support.

The following tables summarize the relevant limitations in a minimum hardware environment:

Table 4-1 Minimum configuration: features

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                               Diskless                Diskless
                               Clients    Disk based   NFS        Client
 Feature             Servers   (Static)   Clients      Clients    Controllers
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 OS RAM usage∗       n/a       1.41MB     1.45MB       1.77MB     2.0MB
 Application RAM∗∗   n/a       2.59MB     2.55MB       2.23MB     2.0MB
 OS disk usage       12MB∗∗∗   n/a        18MB+        2MB++      20MB++
 Login               yes       no         no           no         no

∗

This includes the kernel memory for 15 application processes. Each application process uses 12KB (static linking) or 16KB (DLL linking) of kernel memory. If fewer processes are required, the footprint will diminish. For example, a diskless client using static linking with two applications will have a footprint of 1.26MB.

∗∗

This assumes 4MB of available memory on a client.

∗∗∗

This is the amount required for the server supplement installation. Each POS disk based client template to be hosted requires 4.5MB plus 250KB per client. Each diskless client template requires 1.5MB plus 10KB per client.

+

This assumes the default swap filesystem size of 15MB.

++

Disk usage on the server. Note also that a diskless POS client with NFS root can page application process text pages from the server.

++

Client controller disk usage is the same as that for normal disk based usage plus 2MB for logs. Add 4.5MB per disk based template and 250K per disk based client, and 1.5MB per diskless template.

Table 4-2 Minimum configuration: additional functionality

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                       Diskless Client Size   Disk based Client Size
 Added Functionality   Increase (DLL)         Increase
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 IBM 4690              960KB                  280KB
 X, no mouse           2.39MB
 X, with mouse         2.42MB
 NetBIOS               436KB
 SNMP                  604KB
 NFS (non-root)        568KB
 SLIP                  n/a                    240KB
 PPP                   n/a                    640KB