Oracle Odbc Driver Enable Closing Cursors

Tom, What is connection pooling. Please, can you give an example s that show thorough understanding of the subject matter as related to either ODBC OR JDBC.

21.2.1.1 What is the Oracle ODBC Driver. The Oracle ODBC Driver enables ODBC applications on Microsoft Windows, as well as UNIX platforms like Linux, Solaris, and вЂ.

RESTRICTED SESSION Specifies whether logon to Oracle is restricted ENABLE Qllows only users with.

To many open cursors

SumanRoy wrote:

I just want to know in this context, that there is a way to close the explicit cursors, but what is the way to close the implicit cursors in application codes to overcome this error to raise.Some basics first. All SQLs, every single one that is send to the Oracle SQL engine, is parsed into a cursor and a cursor handle returned to the caller.

So cursors are a fact of life when using SQL. The client be that TOAD, SQL Plus, Java or even the PL engine of PL/SQL needs to correctly handle these cursor handles returned by the SQL engine.

PL/SQL is seldom a problem. What happens with a SQL statement like this in PL/SQL.:

declare

  cnt number;

begin

  select count into cnt from emp;

end;The code is written without any reference to a cursor. Thus the PL engine will create an implicit cursor variable, do the fetch from the cursor, store the result in the cnt variable, and close the cursor. All done in fully automated fashion.

Should the code unit fail, that implicit cursor variable will be closed by the PL engine when it goes out of scope.

The following is an explicit cursor:

  cursor c is select count from emp;

  open c;

  fetch c into cnt;

  close c;

end;As you code an actual cursor variable, the PL engine will store the cursor handle it get from the SQL engine into that variable - allowing you to explicitly reference and use e.g. fetch from this cursor variable. Thus it is called an explicit cursor.

You should close it when done. However, the PL engine will automatically close it for you when the variable goes out of scope.

Thus cursor leakage cannot happen with implicit cursor variables and is quite difficult to do using explicit cursors.

But clients like Java and others cannot use PL/SQL s implicit or explicit cursor variable. For the PL engine to pass a usable cursor handle to Java/others, it need to make use of a reference cursor allowing the client to reference the actual SQL cursor in the SQL engine.

And this is where the cursor leakage problem typically occurs. PL is used to create reference cursors. These cursor variables are global to that session as the client must be able to use them. They are only closed when an actual close cursor command is issued - or when the client terminates the session and these cursor variables go out of scope.

When using an application server, a pool of Oracle server sessions are created. These usually existing for the entire lifespan of that application server. Which means these sessions are used again and again and again. And should the client code use ref cursors and not close them, these sessions will soon own 100 s of open cursors that the client code has used, but failed to close.

And this is the usual cause for the too many open cursors error. It is caused by the client that is given a cursor by the server, the cursor is used by the client, but the client never tells the server when it has completed with that cursor so that it can be closed.

Java Database Connectivity JDBC is a method of Java calling SQL and PL/SQL. The DML operations of SELECT, INSERT, UPDATE, and DELETE as well as calling вЂ.

E.1 Features Not Supported. Oracle ODBC Driver does not support the following ODBC 3.0 features: Interval data types. SQL_C_UBIGINT and SQL_C_SBIGINT C data type.