Step 7, Step Ii: Changing And Loading User Program - Siemens SIMATIC S7-400H Manual

10.5.2

STEP 7, Step II: Changing and Loading User Program

Initial situation
The fault-tolerant system is working in the Redundant system mode.
Restrictions
Caution
!
Structural modifications to an FB interface or the instance data of an FB are not
possible in the Redundant system mode and result in the system mode Stop (both
CPUs in STOP mode).
Procedure
1. Perform only the program modifications relating to the hardware to be
removed.
You can add, modify or remove OBs, FBs, FCs and DBs.
2. Load only the program modifications into the PLC.
Result
The fault-tolerant system continues to work in the Redundant system mode. The
modified user program will no longer attempt to access the hardware to be
removed.
S7-400H Programmable Controller Fault-Tolerant Systems
A5E00068197-04
Modifications to the System while in Operation
10-35