A mirror test is conducted in the lab based on onsite logs and the problem symptom. The test result shows that some BTSs reset after XPUs are switched over multiple times.
BSC commissioning methods are then used in the lab to print BTS data on the standby XPU. Comparison of the BTS data indicates the following information:
Data blocks for BTSs that do not reset
Data blocks for BTSs that reset
In the data blocks of the BTSs that reset, the backup flag for the standby board is 0 instead of 43947 (0xABAB). The flag 0 indicates that backup fails, and the flag 43947 indicates that backup succeeds. In this situation, the BTS with a backup failure needs to reset for initialization.
Then, BSC experts responsible for different fields are coordinated to check and troubleshoot the backup mechanism and code. The check result shows that the code for a processing procedure has defects, which may cause a backup failure. As a result, some BTSs reset.
The backup mechanism is then optimized in the lab, and the BSC of a debug version is used for tests. The tests show that the problem has been resolved, and problem locating is complete.