Thank you Pix, for your response.
I don’t Know what happens for foreign MS. Notice that a new roaming agreement was made with a foreign operator few days before the trouble. But I’m not sure that MS from this operator roam in the concerned area(it’s a new operator and this border area is far from the main towns).
The site is a S112 and the problem is more serious for the one TRX sectors. For them there is no need to set a priority they carry the sdcch.
I give you some statistics, that could help for further analysis. The comparison is made between two date, before and after the problem.
Random access attempt:
369257 vs 441223
Random access success:
23,17 vs 58,2 (increase during the problem)
seizure attempts:85623 vs 255732
congestion(%):0.16 vs 26.33
time congestion(%):0.03 vs 7.03
success at seizure(%):81.58vs55.02
drop(%): 6.17 vs 45.77
mean holding time:6.29s vs 11.15s
attempts:80800 vs 247715
success(%): 83.99 vs 33.38
The site is located on a remote BSC and is not at my location, so I’m not able to make abis traces and drive test, but if the cause cannot be find without I’ll go there.