Maximum open_cusors exceed error in oracle

Question

I am returning resultset object from many of my functions.After I run a few programmes i get "maximum no of cursors exceeded in oracle" error. I am not closing Statement obj also i am not closing reultset obj.Which one is to be closed to remove the above error. Also wont garbage collection of the statement which created the resultset in the called function cause my result to cease in existence . Also if i try to use getStatement() in the calling function i get a " operation not allowed " error
What is the solution to my problem
public Statement getStates(){
Connection conn = null;
SharedConnectionPool moConnPool = SharedConnectionPool.getInstance();
ResultSet rsStateMast = null;
ResultSet returnRSStateMast = null;
Statement stmtStateMast = null;
try{
//Get state details
conn = moConnPool.getConnection();
stmtStateMast = conn.createStatement();
String msStateMastQuery = "select csm_state_code, csm_state_name from cms_state_mast where csm_cntry_code = " + this.miCountryCode + "order by csm_state_name";
moLogFile.writeToLog(CLASS_NAME,35,msStateMastQuery);
rsStateMast = stmtStateMast.executeQuery(msStateMastQuery);
returnRSStateMast = rsStateMast;
// stmtStateMast.close();
if (returnRSStateMast != null){
return stmtStateMast;
}//end of if
}//end of try
catch(SQLException sqe){
throw new CMSException("Some SQL Exception occured " + sqe.toString(),sqe);
}//end of catch
finally{
moConnPool.free(conn);
return stmtStateMast;
}//end of finally
}//end of getStates
Above is the function I am using
I realise that my problem would be solved if I pass Statement to or from the function .
But the problem is the I am more than halfway through the project and the chaging all functions in the above manner will be too time consuming . Is there no other solution ? . Why does the getStatement() method in ResultSet give a "method not supported Exception".
Also will the statement obj in the called function be eligible for garbage collection ? Because that will close my ResultSet.
I have already increased the limit of open cursors.
What I want to know is ,whether closing all resultSets will sufficient for closing the open_cursors in Oracle or is it necessary to close all statements to close the open_cursors.
In short whether cursors are related to statements or are they related to Resultsets.
Also I want to know why are my resultSets and statements not getting garbage collected.Because if they would get Garbage collected then they would get closed ,and thus the open_cursors would be closed too.
But then if the statement in the called func gets garbage collected while the resultSet object is still in use , then the resultSet would become null and a null pointer Exception will be thrown.
Considering all this, do you feel it is mandatory for me to pass statements between the functions ? or is there any other awy out?
Also why am i getting an "operation not allowed" exception when I try to use the function rs.getStatement() in order to get the parent statement so that it can be closed in the calling function.

Answer 1

I am returning resultset object from many of my
functions.After I run a few programmes i get "maximum
no of cursors exceeded in oracle" error. I am not
closing Statement obj also i am not closing reultset
obj.Which one is to be closed to remove the above
error. Also wont garbage collection of the statement
which created the resultset in the called function
cause my result to cease in existence . Also if i try
to use getStatement() in the calling function i get a
" operation not allowed " error
What is the solution to my problem
public Statement getStates(){
Connection conn = null;
SharedConnectionPool moConnPool =
SharedConnectionPool.getInstance();
ResultSet rsStateMast = null;
ResultSet returnRSStateMast = null;
Statement stmtStateMast = null;
try{
//Get state details
conn = moConnPool.getConnection();
stmtStateMast = conn.createStatement();
String msStateMastQuery = "select csm_state_code,
csm_state_name from cms_state_mast where
csm_cntry_code = " + this.miCountryCode + "order by
csm_state_name";
moLogFile.writeToLog(CLASS_NAME,35,msStateMastQuery);
rsStateMast =
stmtStateMast.executeQuery(msStateMastQuery);
returnRSStateMast = rsStateMast;
// stmtStateMast.close();
if (returnRSStateMast != null){
return stmtStateMast;
}//end of if
}//end of try
catch(SQLException sqe){
throw new CMSException("Some SQL Exception occured " +
sqe.toString(),sqe);
}//end of catch
finally{
moConnPool.free(conn);
return stmtStateMast;
}//end of finally
}//end of getStates
Above is the function I am using
I realise that my problem would be solved if I pass
Statement to or from the function .Yes, you should close the statement. I used to have the same problem, and close the statement can fix it.
>
But the problem is the I am more than halfway through
the project and the chaging all functions in the above
manner will be too time consuming . Is there no other
solution ? . Why does the getStatement() method in
ResultSet give a "method not supported Exception".
Also will the statement obj in the called function be
eligible for garbage collection ? Because that will
close my ResultSet.
Afraid not, as connection object may hold a reference to it, and connection objects are in a pool, so the statement object will be there as long as the connection object's there.
>
I have already increased the limit of open cursors.
What I want to know is ,whether closing all resultSets
will sufficient for closing the open_cursors in Oracle
or is it necessary to close all statements to close
the open_cursors.
Well, I don't know the inside code, but, as I experienced, the problem is you openned too many statement (conn.createStatement()), because you are using a connection pool, you may re-use a connection object many times, this is kind of like this:
conn.createStatement();
conn.createStatement();
..//a lot of themso you opened too many statement, and I suspect this is the problem according to my testing.
In short whether cursors are related to statements or
are they related to Resultsets.
If you close the statement, the result set of it will be closed as well, but I don't think close result set could close statement.
Also I want to know why are my resultSets and
statements not getting garbage collected.Because if
they would get Garbage collected then they would get
closed ,and thus the open_cursors would be closed
too.
As I mentioned above, because you're using a connection pool, and unless you explicitly close statement object, its reference my be hold by the connection object and won't be garbage collected.
But then if the statement in the called func gets
garbage collected while the resultSet object is still
in use , then the resultSet would become null and a
null pointer Exception will be thrown.
The statement is still there.
Considering all this, do you feel it is mandatory for
me to pass statements between the functions ? or is
there any other awy out?
Usually, you should return a collection (like HashTable or Vector etc.) instead of the result set, so, you can have one point control over the statement and result set object. But in you case, you have to track each statement object and close it.
Also why am i getting an "operation not allowed"
exception when I try to use the function
rs.getStatement() in order to get the parent statement
so that it can be closed in the calling function.
This is not supported, at least in the libarary you're using.