Do Asterisk1-2-1 Support Realtime Dialplan?

i am a freshman to this field and very intrested in it.
Recently I install the asterisk1-2-1 and during the configuration,I could not make the server offer Realtime Dialplan Service.
The cofiguration follows:

the extconfig.conf:
extensions => odbc,asterisk,extensions_conf
iaxusers => odbc,asterisk,iaxfriends
sipusers => odbc,asterisk,sipfriends

when in use,the iaxusers and sipusers works,but the extensions failed.
Only after the modification:
extensions.conf => odbc,asterisk,extensions_conf
the extensions works.But it is not realtime.

How could i do ?