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

Modifying the System During Operation
11.5.2

STEP 7, Step II: Changing and Loading User Program

Initial situation
The fault-tolerant system is working in redundant system mode.
Restrictions
Caution
!
Structural modifications to an FB interface or the instance data of an FB are not
possible in 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 redundant system mode. The
modified user program will no longer attempt to access the hardware to be
removed.
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Automation System S7-400H Fault-tolerant Systems
A5E00068197-07