Guardian Application Conversion Guide

Conversion Strategy
Introduction
1–4 096047 Tandem Computers Incorporated
Figure 1-1. D-Series Operating System Environment
High-PIN Processes: PINs ≥ 256
Low-PIN Processes: PINs 0 – 254
User
Applications
User
Applications
Tandem
Subsystems
Operating
System
Operating
System
Tandem
Subsystems
PIN 255 is reserved.
Converted Process
Unconverted Process
Operating
System
Tandem
Subsystems
Conversion Strategy Converting application programs includes those activities that allow you to change
C-series applications to take advantage of the D-series enhancements. Migrating
application programs includes those activities that allow you to run C-series
applications on D-series systems.
Almost all applications designed to run under the C-series operating system can
migrate without modification to run under the D-series operating system by
continuing to use the C-series-compatible interface. The exceptions are few and are
detailed in Appendix D, “Considerations for Migrating Any Application.” Therefore,
there is usually no need to do any conversion unless your system has reached or is
likely to reach the C-series limit of 255 concurrent processes.
If you might reach the C-series limit of 255 processes, then you need to move some
processes into high PINs. Tandem recommends converting your applications if, after
placing Tandem and third-party products in high PINs, you still need more process
control blocks (PCBs) in the low-PIN range than are available.
To move processes into a high PIN requires conversion, because the process identifiers
used in the C-series-compatible interface allow for only 8-bit PINs.
The amount of conversion you need to do depends on the type of application. Single-
process applications, for example, are easier to convert than multiple-process
applications, and some multiple-process applications need more conversion effort than
others.