Hi
We have an APEX 5.0.3.00.03 app running in Oracle 12c (12.1.0.2.0 64bit)
Recently the system crashed with ORA-00020: maximum number of processes (300) exceeded.
DBAs restarted the database setting the value to 600

On restart I logged onto the APEX app and into Toad and ran the following on the database
select * from v$session
this gave 173 processes

The database is only used by APEX applications.

I have been monitoring this number for the last 2 days and as the APEX app is used I can see it goes up by a few then down.
It currently stands at 175 with 2 users logged into the APEX app.

Also running the following:
select username, count(*)
from v$session
group by rollup(username);

gives
USERNAME COUNT(*)
AMIS 2
AMIS_RO 2
APEX_LISTENER 40
APEX_PUBLIC_USER 40
APEX_REST_PUBLIC_USER 40
DBSNMP 2
ORDS_PUBLIC_USER 10
39
175

Can someone please explain why we have so many processes running from startup of the database and also why APEX seems to be creating so many processes that it eventually exceeds the level and brings the system down. We have seen this issue several times previously in dev environments but this is the first time in production.

Is there any setting or something else that we should be doing to stop/limit the number of processes on this database.

Thanks for any help.