Guardian Application Conversion Guide

More Concurrent Processes per CPU
Introduction
096047 Tandem Computers Incorporated 1–3
Other changes
To support its extended features, the D-series operating system also provides new
file-system error numbers, file-system error lists, and object-file attributes.
Section 2, “Conversion Concepts,” describes these differences in detail.
Note There are two programmable interfaces to a D-series system:
The C-series-compatible interface. You cannot make use of the extended system limits using this
interface. Entities that describe parts of the C-series-compatible interface are generally referred to in
this guide as C-series entities.
The D-series enhanced interface, which supports the new system limits as described earlier. Entities
that form parts of the D-series enhanced interface are referred to in this guide as D-series entities.
A program that runs on a D-series system can use either or both of these interfaces.
More Concurrent
Processes per CPU
Although the D-series operating system increases several software limits, the limit that
most directly affects an application is the number of concurrent processes per CPU. A
D-series operating system can support an architectural limit of 65,534 concurrent
processes per CPU. The actual number of concurrent processes per CPU depends on
the system’s available resources, such as virtual memory.
The system identifies a process by a process identification number (PIN). When the
system creates a new process, it assigns a PIN to the process. A C-series PIN ranges
from 0 through 255 (and therefore can be represented in an 8-bit field). A D-series PIN
ranges from 0 through the maximum number of processes per CPU supported by the
system. A D-series PIN falls in these categories:
A low PIN ranges from 0 through 254.
A high PIN ranges from 256 through the maximum number supported for the
CPU.
PIN 255 is never assigned to a process. It is sometimes used in a synthetic process ID,
which is described in Appendix C.
Figure 1-1 shows various converted and unconverted processes running in a CPU in
the D-series operating system environment.