behavior CPU after failure

If synchronization is lost during redundant mode, the standby CPU (RACK1) changes to ERRORSEARCH mode. The other CPU (RACK0) remains master and continues operation in standalone mode. After that I switched off power of PS (RACK0). Next one I want to start up CPU (RACK1). but I cannot start up CPU (RACK1) - Event 4xA4 ("The configurations of the individual CPUs and/or other modules are not compatible with each other").

Can I run my CPU (RACK1) in standalone mode without ES?

Hi, 

Upload the entire Diagnostic buffer to see clearly what is happening. How is the ERROR-SEARCH mode completes? 

For detailed explanation check the SIMATIC Fault-tolerant systems S7-400H maual under chapter "11.3.6 ERROR-SEARCH mode". I would like to highlight something from this manual:

 "The purpose of ERROR-SEARCH mode is to find a faulty CPU. The standby CPU runs the full self-test, while the master CPU remains in RUN. If a hardware fault is detected, the CPU changes to DEFECTIVE state. If no fault is detected the CPU is linked up again. The faulttolerant system resumes the redundant system state. An automatic master-standby changeover then takes place. This ensures that when the next error is detected in errorsearch mode, the hardware of the previous master CPU is tested."

So make sure you give enough time to this procedure to complete. 

After the end of ERROR-SEARCH mode, CPU memory in RACK1 was cleared. So the CPU wasn't able to run. I cannot find this behavior of CPU in manual "STEP 7 - Fault-Tolerant Systems".

If I use FLASH memory, CPU can run after failure of synchronization. Because load memory is not cleared.

Hi,

Looks like the CPU initiated a Memory Reset after Error Search mode. 

Please upload the diag buffer so we can have a closer look.

Hi, 

Check out your sync module. See Event 10 in your buffer:

Event 10 of 40:  Event ID 16# 7955

SYNC submodule error .... 

I hope I could help!