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Overview of Quantum Hot Standby
30
840 USE 106 00 January 2003
Application size For basic mechanisms (data and program transfer), the IEC HSBY and the 984
HSBY system operate in the same manner. The data transfer during normal
operation, accomplished by copying the state RAM from the Primary to the Standby,
causes differences in terms of application size. In IEC HSBY, a part of the state RAM
is used to transport the IEC application data from the Primary to the Standby.
Therefore the size of IEC application data cannot exceed the configured size of the
state RAM itself. The absolute maximum for IEC application data is 128K (64K
words of state RAM). For the size of an IEC application’s executable code there is
also a limit of 568K under Concept 2.1/2.2. The IEC application’s executable code
limit was increased to 1 Megabyte for Concept 2.5.
Quantum IEC Hot
Standby
Overview
IEC Language programs only, no 984 Ladder Logic permitted
To bring a Standby on-line
Primary and Standby controller executives must be equal.
Primary and Standby IEC Projects must have the same name and the
applications must be equal.
On-line changes to the Primary are permitted
With Concept 2.1/2.2, the Standby controller is taken off-line as soon as the
first Primary on-line change is made. The Primary program must be
transferred to the Standby before it can be brought back on-line.
Concept 2.5 supports Logic Mismatch in the Hot Standby configuration
extension. This option allows the Standby controller to remain online with a
different program than the primary controller.
Primary controller on-line changes may include
Addition of sections
Addition of DFBs allows pre-qualification of user changes in an office
environment
Logic Mismatch
With Concept 2.1/2.2, it is not possible to load a new version of the application
on Standby, bring it on-line, and transfer control to make it the new Primary.
Under Concept 2.5, with Logic Mismatch enabled, a new version of the
application can be downloaded to the Standby controller and brought online.
Control can then be transferred to the Standby controller to make it the new
Primary controller.
To upgrade the controller Execs
With Concept 2.1/2.2, the process must be stopped. Then Primary and
Standby controllers must be stopped and downloaded individually.
Under Concept 2.5, the controller executives can be upgraded while the
process continues to run.