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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Cats, Pigeons and Open Cursors
Justin
I agree with you 99%. My only quibble is with your statement "relatively easy to walk through the code". I won't pass myself off as a Java expert, but just want to point out that OOP like Java have a much more complex execution path than the older procedural languages most of us are familiar with. Transaction boundaries become very difficult to delineate, especially with event-driven GUI interfaces. Then there are things like J2EE that can handle database access automagically. Part of the value of modern development environments like Java is to utilize code others have written rather than writing every line of code yourself like most of us did in the older languages. I'm not denying that it may be necessary in some situations for the execution path to be traced in detail to determine the problem, just that the "relatively easy" may not be quite the case.
Dennis Williams
DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Justin Cave
Sent: Tuesday, June 08, 2004 4:57 AM
To: oracle-l_at_freelists.org
Subject: RE: Cats, Pigeons and Open Cursors
I think you are running into a fundamental problem. Once you return a cursor to the Java application, the Java application owns it. Oracle doesn't generally allow you to come along and kill things owned by another session.
The only ways I'm aware of to close the cursor would be to do so in the Java application or to kill the entire session from PL/SQL. If your Java developers are moderately competent, it should be relatively easy to walk through the code and ensure that all the cursors are closed by the appropriate exception block. If there are a few corner cases where cursors are not closed, you can cycle connections from the connection pool or close long-open connections from PL/SQL. The former option will probably cause your Java application fewer problems.
Justin Cave
Distributed Database Consulting, Inc.
http://www.ddbcinc.com/askDDBC
-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org]
On Behalf Of Piet de Visser
Sent: Tuesday, June 08, 2004 3:31 AM
To: oracle-l_at_freelists.org
Subject: Cats, Pigeons and Open Cursors
List,
We have a nice problem between Java and Pl/sql, and since PL/sql is slightly out of my comfort zone, I'm submitting it to the list (fairly sure we are not the first to stumble on this).
A procedure is used to open an number of ref-cursors and pass them back to
java as out-parameters.
Which cursors are opened varies and depends on in-parameters.
When Java is done using the cursors,
it Should close all the opened cursors.
Sometimes the closing is skipped or forgotten, and the nr-open-cursors
increases rapidly.
Since connections are rarely closed,
but rather re-used, the db runs out of open cursors.
Given the fact that we do not quite trust the Java code to always close all cursors, we would like to build a sure-fire way in Pl/sql to close all previously opened cursors.
First suggestion was to create another procedure that checks all cursors
using ISOPEN%cursor123 and closes them.
This doesn't work because REF-cursors can apparently not be declared outside
of functions or procedures.
Question:
More precisely, we want the package to keep track of all cursors it has opened (we can keep a list, no problem if that requires some extra code). We then want the same procedure or another procedure to go in, read the list of open cursors, an close any that are still open.
Is this feasible ?
Suggestions anyone ?
Regards,
PdV
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