Listener drops suddenly or refuses connection

Question

I am having some strange problems and need some help ASAP.
I have an Oracle 7.3.4 database running on AIX 4.3. Now the listener sometimes suddenly stops for no apparent reason or refuses connection requests to the database leading to
ORA-12203 TNS: unable to connect destination
errors even though on checking the status of the listener it indicates that it's still up.
Now does the SNMP setting affect the operation of the listener in any way. It's currently set to ON.
Thanks all.

Answer 1

Yes I do. infact i have spent virtually the whole day stopping and starting the listener. Haven't left my desk at all.
Before it ran almost uninterrupted but now i have to constantly monitor it. Sometimes it works, sometimes it doesn't.
when i restart it, i have something like this
cmsxd has i service handler(s)
even before i restart my Pro*C application cycle, the number of service handlers begins to rise and always hits a maximum of 13 after which it doesn't rise anymore. There is nothing happening as yet but it still rises. If a service handler is a db instance registered with a listener and i only have one db instance i.e cmsxd, why would i have 13 now?
I do not know what these service handlers or db instances are. The lsnrctl status command does not give a detailed breakdown of these service handlers.
when i type lsnrctl services i get the ff output
Services Summary...
cmsxd has 13 service handler(s)
DEDICATED SERVER established:11 refused:0
DISPATCHER established:12 refused:0 current:28 max:252 state:ready
D000 (machine: cepsvr, pid: 23478)
(ADDRESS=(PROTOCOL=ipc)(DEV=15)(KEY=#23478.1))
DISPATCHER established:8 refused:0 current:28 max:252 state:ready
D001 (machine: cepsvr, pid: 23736)
(ADDRESS=(PROTOCOL=ipc)(DEV=15)(KEY=#23736.2))
DISPATCHER established:45 refused:0 current:24 max:252 state:ready
D002 (machine: cepsvr, pid: 23994)
(ADDRESS=(PROTOCOL=ipc)(DEV=15)(KEY=#23994.2))
DISPATCHER established:28 refused:0 current:28 max:252 state:ready
D001 (machine: gcsvr, pid: 23258)
(ADDRESS=(PROTOCOL=ipc)(DEV=15)(KEY=#23258.1))
DISPATCHER established:0 refused:0 current:1 max:252 state:ready
D003 (machine: cepsvr, pid: 24252)
(ADDRESS=(PROTOCOL=tcp)(DEV=15)(HOST=192.168.0.5)(PORT=32787))
DISPATCHER established:0 refused:0 current:1 max:252 state:ready
D004 (machine: cepsvr, pid: 24510)
(ADDRESS=(PROTOCOL=tcp)(DEV=15)(HOST=192.168.0.5)(PORT=32788))
DISPATCHER established:0 refused:0 current:0 max:252 state:ready
D005 (machine: cepsvr, pid: 24768)
(ADDRESS=(PROTOCOL=tcp)(DEV=15)(HOST=192.168.0.5)(PORT=32789))
DISPATCHER established:0 refused:0 current:0 max:252 state:ready
D004 (machine: gcsvr, pid: 18970)
(ADDRESS=(PROTOCOL=tcp)(DEV=15)(HOST=192.168.1.1)(PORT=32919))
DISPATCHER established:28 refused:0 current:0 max:252 state:ready
D000 (machine: gcsvr, pid: 20946)
(ADDRESS=(PROTOCOL=ipc)(DEV=15)(KEY=#20946.1))
DISPATCHER established:0 refused:0 current:0 max:252 state:ready
D003 (machine: gcsvr, pid: 19592)
(ADDRESS=(PROTOCOL=tcp)(DEV=15)(HOST=192.168.1.1)(PORT=32918))
DISPATCHER established:27 refused:0 current:0 max:252 state:ready
D002 (machine: gcsvr, pid: 19922)
(ADDRESS=(PROTOCOL=ipc)(DEV=15)(KEY=#19922.1))
DISPATCHER established:0 refused:0 current:0 max:252 state:ready
D005 (machine: gcsvr, pid: 22048)
(ADDRESS=(PROTOCOL=tcp)(DEV=15)(HOST=192.168.1.1)(PORT=32925))
my database is on cepsvr and gcsvr is another server that has a connection to cepsvr.
Thanks for your replies.