thanks again for the answer.
We changed the parameter from 100 to 1000, as 10000 (default) didn’t accept it in MFS. After changing it, all GP boards had to be reset and when all cells were normalized we noticed an improvement in a throughput, gprs attachment was ok etc. But only for few hours. Again, the problems were appeared and we had to add GP board and extending number of AterMux to maximum (we didn’t want to experiment with the parameter anymore, I would like to know what is the value of this param N_DATA_BYTES_MAX_TRANS_PERIODIC in other Alcatel-Lucent networks). After that, there were no more problems, no more CPU congestion.
So, in these cases I think that changing parameters is not so helpful for decreasing congestion of CPU (it was over 60%).