More on "maximum open cursors exceeded"

Question

It seems a lot of people have been seeing this error message, but reading through the posts on the topic hasn't given me any new insight on the problem. Here's an account of my particular situation:
I am using the XSQL servlet, v.1.0.0.0 with the thin jdbc driver v.1.x. The servlet is running within an Apache server (1.3.12) on a Linux box, and the Oracle database (8.1.5) is located on a Solaris 2.6 machine.
The servlet accepts HTTP connections, performs the corresponding SQL queries and returns the output from the database to the HTTP client. Here's a simple example:
(Sorry about potential bad line breaks.)
client request:
% telnet xsql-host.some.domain 80
Trying xxx.xxx.xxx.xxx
Connected to xsql-host.some.domain.
GET /xsql/test/listall.xsql
<server response here>
listall.xsql:
<?xml version="1.0"?>
<page connection="boss" xmlns:xsql="urn:oracle-xsql">
<accounts>
<xsql:query tag-case="lower" rowset-element="" row-element="accountinfo">
select * from test
</xsql:query>
</accounts>
</page>
Very simple stuff indeed. Now, this has worked perfectly for 3 weeks or so. During this period, the xsql servlet has been stopped and restarted numerous times and the machine hosting the database has been rebooted at least three times. Then, for no apparent reason (as nothing had changed in the setup described above), I started getting "maximum open cursors exceeded" on every request. Since then, I have been unable to get the system working as it had up until now. I haven't restarted the database and I would like to avoid doing so, because that would not be a valid solution for us if the problem reappeared in production. The maximum open cursors setting in Oracle should be correct, since things were running smoothly before.
From what I can see, the problem could be with the servlet not closing its cursors. One post mentioned that it did, but I would appreciate it if this could be double-checked. Considering the database is the only portion of the system which has been kept running for extended periods of time, it seems to me that this might indeed be the problem.
Confirmation, workarounds, suggestions, patches, or a consolation box of chocolates would all be appreciated.
Thanks,
- Fad
([email protected])
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Answer 1

Check which process is making all the cursors on which database. If it is your procedure, try explicitly closing the cursors. I think the cursors are only implicitely closed after the transaction is ended. If you loop and open a cursor within the loop, that might be the problem.
I also had this problem with Java working over a JDBC connection some time ago on a 815 database. If I recall correctly, that was caused by the JDBC driver and fixed by replacing it with a JDBC driver of 9i.
The following script is what I used previously in a program that can draw a graph from the results. It is ugly, but does the job.
Hope this helps,
L.
select
  'max cursors',
  to_number(value)
from
  v$parameter
where
  name = 'open_cursors'
union
select
  substr(lower(username),1,10)||'('||substr(to_char(ses.sid)||','
  ||to_char(serial#),1,9)||')',
  s.value
from
  v$sesstat s,
  v$statname n,
  v$session ses
where
s.statistic#=n.statistic#
and ses.sid=s.sid
and n.name like '%cursor%'
and n.name like '%current%'
and not (ses.sid between 1 and 6)