Product : ISaGRAF 3.30

Date    : 1999

File    : Hotrst.Hot Restart management with ISaGRAF 3.30.htm

Subject : Hot Restart management with ISaGRAF 3.30

Keywords: Hot restart


Hot restart of a second CPU used in case of fault detection:


There is an internal feature in ISaGRAF V3.30 kernel software that

enables transmission of data between two CPUs and hot-restart of

the second CPU from transferred data when the first CPU fails.




1- There is a "Master CPU" and a "Slave CPU"

2- The application code is initially downloaded to both CPUs

3- Only the Master CPU starts (the other one is not started)

4- On each cycle, the Master CPU copies or transfers data to

the Slave CPU

5- When a default is detected, the Slave CPU is launched in

"hot restart" mode, using data from the Master CPU


This has been implemented by one ISaGRAF customer, using fast

Ethernet link to transfer data between both CPUs.

This transfer could also be done through shared memory or any other



ISaGRAF provides, at the source level:

1- Hooks in the Master CPU kernel code to activate the transfer

2- Options in the Slave CPU kernel code to start in

"hot restart mode"

3- ISaGRAF provides the full description of what pieces of data have

to be transferred


WARNING! ISaGRAF does not provide any tool for data transfer,

fault detection, slave CPU launching.

This has to be implemented by the integrator.


All hooks and required software are included in the standard

ISaGRAF V3.30 IDK product.

The "Hot Restart" feature is not documented in standard IDK book.

Documentation and explanations can only be provided by

technical support.


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