monitor & trap

I would like to have snmpd sending traps automatically if one file is 
larger than a certain size.  So I added a few lines to snmpd.conf file, 
and the complete snmpd.conf file is attached below. 

Then I started snmpd and snmptrapd daemons on localhost. snmptrapd uses a 
local file as its log by started as 
        "/usr/sbin/snmptrapd -u /var/run/snmptrapd.pid -o 
/home/shannon/trap.log"

However, there was no trap event saved in the log even if the file is 
larger than 1kB, and fileErrorFlag (.1.3.6.1.4.1.2021.15.1.100) has been 
set to 1 according to snmpwalk.

I am using net-snmp 5.0.9 since it is included in RedHat distribution, and 
we may have to stick to this old version.

Could you please help me if you know what is wrong with my configuration? 
Thank you so much.

Shannon

========================================
snmpd.conf
========================================
rwuser  notConfigUser
rwcommunity  notConfigUser
pass    .1.3.6.1.4.1.4413.4.1   /usr/bin/ucd5820stat
file    /home/shannon/snmptest.txt      0.02

trapsink  localhost
trap2sink localhost
informsink  localhost
trapcommunity notConfigUser
authtrapenable  1

monitor  -r 30  "fileSize"  .1.3.6.1.4.1.2021.15.1.100 = 1
trapsink localhost
trap2sink localhost

syslocation     here
syscontact      Shannon
sysservices 72

com2sec notConfigUser  default       public
group   notConfigGroup v1            notConfigUser
group   notConfigGroup v2c           notConfigUser
view    allview       included   .1.3.6
view    systemview    included   .1.3.6.1.2.1.1
view    systemview    included   .1.3.6.1.2.1.25.1.1
access  notConfigGroup ""  any   noauth    exact  allview  none  allview