COBOL Manual for TNS and TNS/R Programs

Process Initiation, Communication, and
Management
HP COBOL Manual for TNS and TNS/R Programs—522555-006
31-2
Memory and Virtual Memory
Topics:
•
Memory and Virtual Memory
•
Initiating a Process From an HP COBOL Program
•
Communicating With a Process
•
Managing a Process
Memory and Virtual Memory
Memory is one resource consumed by a process. Each processor in an HP system has
its own physical memory. Each processor in a system can have one to four increments
of memory, and different processors in the same system can have different amounts of
memory. The size of the increments depends on the type of processor—see the
system description manual for your processor.
The operating environment allows several processes to occupy different areas of
physical memory concurrently. It manages these processes with a virtual memory
mechanism. The active portions of a process reside in physical memory. The inactive
portions remain in physical memory only as long as the number of active processes
remains small. As the number of active processes grows, the inactive portions of
processes tend to remain on disk in virtual memory. The unit of memory allocation is
the page, whose size depends on the processor. See the system description manual
for your processor.
The virtual memory for process code consists of the loadfile.
The virtual memory for process data consists of temporary disk storage, allocated at
the time the process is created.
Figure 31-1. Process Creation, Execution, and Termination
Process Process Process
CPU
Memory
Tables
Resources
PCB Table Entry Resident Memory
Virtual Disk Space
Creation Execution Termination
Allocation Deallocation
Program
File
VST709.vsd