In the trace event did after switch ON monitor, I remark lot of very big time to close a CURSOR.
The select should be a very litle one, the normal time to close it, is about 0.001 second. But sometime (often) it needs more than 12 seconds to 958 seconds.
The system is AIX 5.L Db2 udb V 184.108.40.206 (obtain by db2level)
Thank you for your help