gtpa2m0b | Application Programming |
The TPF system performs the following functions:
- Control of incoming and outgoing messages; receives and transmits
messages over communication lines
- Main storage and file storage management; controls allocation and
release of main and file storage as requested by programs
- Queuing of work to be done; maintains lists of entries waiting for
event completion or further processing
- Priority of processing; reactivates entries on a system priority
basis
- Input/output control; services all input/output operations, usually
upon request of the application programs
- Error checking and error recovery; identifies, logs, and resolves
(where possible) all permanent and transient equipment errors
- Operator communications; communicates with the operator and provides
pertinent information requested by the operator or considered necessary by TPF
- Restart and switchover; provides a means of starting active
operations in a computer system or restarting operations in the standby
system.
Most operating systems perform all of the preceding functions. The
performance differences of each can be attributed in large part to the
concepts employed to do each function. It must be assumed in designing
a real-time, high-availability system that the user's business needs
cannot allow the operating system to be taken down to perform maintenance
functions. TPF facilities therefore are designed, and the user's
applications must be designed, for database update and maintenance to be
performed in real-time and still permit good response time. For the
same considerations, should a system failure occur, the restart process is
rapid and uncomplicated, making most restarts successful and achievable in
seconds.