Strange happenings with examples from Tom Kyte's book. 10 XE

Question

Hi all,
I was twiddling my thumbs and decided to brush up on some of Oracle's fundamentals.
Tom Kyte's book - Effective Oracle by Design. Examples on pp. 141 - 142 (to do with
bind variables). Typed in the example and obtained a very strange system reaction.
It consists of a package "DEMO_141_PKG" with 1 procedure "parse_bind_execute_close"
which is called by the procedure QUICKFIX142.. The system then proceeds to go mental.
If anybody could explain to me what's going on, I would be grateful. I'm running 10 XE on
Ubuntu Linux.
On running the code (below) I get this in the "Run" window of SQLDeveloper.
Connecting to the database demo.
ORA-01000: maximum open cursors exceeded
ORA-06512: at "SYS.DBMS_SYS_SQL", line 884
ORA-06512: at "SYS.DBMS_SQL", line 9
ORA-06512: at "DEMO.DEMO_141_PKG", line 17
ORA-06512: at "DEMO.QUICKFIX142", line 8
ORA-06512: at line 2And the logging window of SQLDevloper just shows a continuous
stream of the text below - I have to kill the sessions as SYS from
within Oracle - the Terminate process from within SQLDeveloper
doesn't manage to kill this runaway process.
Logging output
SEVERE     2474100     1     oracle.dbtools.raptor.runner.DBStarterFactory     logDbmsOutput: ORA-01000: maximum open cursors exceeded
SEVERE     2474099     1     oracle.dbtools.raptor.runner.DBStarterFactory     logDbmsOutput: ORA-01000: maximum open cursors exceeded
SEVERE     2474098     0     oracle.dbtools.raptor.runner.DBStarterFactory     logDbmsOutput: ORA-01000: maximum open cursors exceeded
SEVERE     2474097     0     oracle.dbtools.raptor.runner.DBStarterFactory     logDbmsOutput: ORA-01000: maximum open cursors exceeded
SEVERE     2474096     1     oracle.dbtools.raptor.runner.DBStarterFactory     logDbmsOutput: ORA-01000: maximum open cursors exceeded
<Millions of lines snipped - it just keeps going>Now, the code is here for those who would like to help me get to the bottom of this phenomenon.
create or replace
PACKAGE DEMO_141_PKG AS
procedure parse_bind_execute_close(p_input in varchar2);
END DEMO_141_PKG;
create or replace
PACKAGE BODY DEMO_141_PKG AS
  g_first_time boolean := TRUE;
  g_cursor number;
procedure parse_bind_execute_close(p_input in varchar2)
AS
  l_cursor number;
  l_output varchar2(4000);
  l_status number;
BEGIN
  l_cursor := dbms_sql.open_cursor;
  dbms_sql.parse(l_cursor, 'SELECT * FROM Dual WHERE Dummy = :x', dbms_sql.native);
  dbms_sql.bind_variable(l_cursor, ':x', p_input);
  dbms_sql.define_column(l_cursor, 1, l_output, 4000);
  l_status := dbms_sql.execute(l_cursor);
  if(dbms_sql.fetch_rows(l_cursor) <= 0)
  then
    l_output := null;
  else
    dbms_sql.column_value(l_cursor, 1, l_output);
  end if;
END parse_bind_execute_close;
END DEMO_141_PKG;and the above is called here
create or replace
PROCEDURE QUICKFIX142 AS
BEGIN
-- demo.runstats_pkg.rs_start; // Don't worry about  runstats - it's a Tom Kyte package for
-- timings and measuring contention.
  execute immediate 'alter session set session_cached_cursors = 0';
  for i in 1..1000
  loop
    DEMO_141_PKG.parse_bind_execute_close('Y');
  end loop;
-- runstats_pkg.rs_middle;
  execute immediate 'alter session set session_cached_cursors = 100';  // reduced this to 50, 20, 10 & 5 - no effect.
  for i in 1..1000
  loop
    DEMO_141_PKG.parse_bind_execute_close('Y');
  end loop;
-- runstats_pkg.rs_stop;
END QUICKFIX142;Edited by: Paulie on Aug 12, 2011 2:18 PM

Answer 1

If you modify the called package by adding :
  -- CLOSE THE CURSOR
  dbms_sql.close_cursor(l_cursor);in
procedure parse_bind_execute_close(p_input in varchar2)
AS
  l_cursor number;
  l_output varchar2(4000);
  l_status number;
BEGIN
  l_cursor := dbms_sql.open_cursor;
  dbms_sql.parse(l_cursor, 'SELECT * FROM Dual WHERE Dummy = :x', dbms_sql.native);
  dbms_sql.bind_variable(l_cursor, ':x', p_input);
  dbms_sql.define_column(l_cursor, 1, l_output, 4000);
  l_status := dbms_sql.execute(l_cursor);
  if(dbms_sql.fetch_rows(l_cursor) <= 0)
  then
    l_output := null;
  else
    dbms_sql.column_value(l_cursor, 1, l_output);
  end if;
  -- CLOSE THE CURSOR
  dbms_sql.close_cursor(l_cursor);
END parse_bind_execute_close;
END DEMO_141_PKG;Then script runs with default OPEN_CURSORS setting:
SQL> connect / as sysdba
Connected.
SQL> show parameter open_c
NAME                                 TYPE        VALUE
open_cursors                         integer     300
SQL> connect test/test
Connected.
SQL> exec quickfix142;
PL/SQL procedure successfully completed.