High waiting events appear: SQL*Net more data from client

Hello,

I would like to identify the root cause of the number of events "sql*net more data from client" that appears from 12th january.

There are NOT sql_id or program related, we only find machines and samples in the dba_hist_active_sess_history view:

select

TO_CHAR(S.BEGIN_INTERVAL_TIME,'yyyy-mm-dd') dia,

event,machine,count(*)

from DBA_HIST_ACTIVE_SESS_HISTORY sql,

dba_hist_snapshot s

WHERE

S.SNAP_ID = SQL.SNAP_ID

and s.dbid = sql.dbid

and s.instance_number=sql.instance_number

and event like'%from client'

group by TO_CHAR(S.BEGIN_INTERVAL_TIME,'yyyy-mm-dd'),event,machine