DBMS_SCHEDULER and CALL statement

This is a brief reminder for those using intensively Oracle dbms_scheduler package to schedule a launch of a stored PL/SQL procedure. Recently I was investigating a wide range performance problem via a 60 minutes AWR snapshot until the following action that appears in the TOP SQL ordered by Gets has captured my attention:

SQL ordered by Gets

Buffer Gets	Executions	Gets per Exec	%Total	Elapsed Time (s)	%CPU	%IO	SQL Id	SQL Module	SQL Text
858,389,984	2	429,194,992.00	89.58	3,606.79	97.2	1.9	6cjn7jnzpc160	DBMS_SCHEDULER	call xxx_PA_REDPC.P_EXPORT_DA…
542,731,679	32,021	16,949.24	56.64	3,201.40	98.4	.6	4bnh2nc4shkz3	w3wp.exe	SELECT WAGD_ID FROM S1

It is not the enormous Logical I/O done by this scheduled stored procedure that has retained my attention but it is the appearance of the call statement in the corresponding SQL Text.

Where does this come from?

Let’s get the DDL of the corresponding program

 SELECT dbms_metadata.get_ddl('PROCOBJ','XXX_PARSE_MESSAGE_PRG', 'SXXX') from dual;

Which gives this

 BEGIN
  DBMS_SCHEDULER.CREATE_PROGRAM
    (program_name         => 'XXX_PARSE_MESSAGE_PRG'
    ,program_type         => 'STORED_PROCEDURE'
    ,program_action       => 'XXX_PA_REDPC.P_EXPORT_DA.P_xxxx'
    ,number_of_arguments  => 0
    ,enabled              => FALSE
    ,comments             => NULL);
 COMMIT;
 END;
 /
 

I have  arranged a little bit the generated DDL script for clarity.

Now things become clear.

When you define your program using

     program_type         => 'STORED_PROCEDURE'
 

Then your job will be executed using the SQL command call

    call XXX_PA_REDPC.P_EXPORT_DA..'
 

This is in contrast to when you define your program using

  program_type         => 'PLSQL_BLOCK'
 

which has the consequence of making your job being executed using an anonymous PL/SQL block

 BEGIN
    XXX_PA_REDPC.P_EXPORT_DA..
 END;
 

And now the question: how would you prefer your scheduled stored procedure to be executed?

1. via the  SQL call statement
2. via the anonymous PL/SQL block

Well, after a brief research on My Oracle support I found a bug that seems closely related to it

DBMS_SCHEDULER Is Suppressing NO_DATA_FOUND Exceptions for Jobs that Execute Stored Procedures (Doc ID 1331778.1)

In fact, there is one fundamental threat when opting for the call statement. Consider this

 SQL> create or replace procedure p1 as
    begin
     insert into t values (1,2);
      raise no_data_found;
      commit;
    end;
 /
Procedure created.

SQL> select count(1) from t;   

   COUNT(1)
   ----------        
    0

I am going to call this procedure using the call statement which normally will raise a no_data_found exception and the inserted data into table t will be rolled back

SQL> call p1();

Call completed.

SQL> select * from t;

        N1         N2
---------- ----------
         1          2

Despite the raise of the no_data_found exception inserted data has been committed and the exception ignored. This will not have happened if I have managed to execute the stored procedure using an anonymous PL/SQL block as shown below:

SQL> truncate table t;

Table truncated.

SQL> begin
p1();
end;
/
begin
*
ERROR at line 1:
ORA-01403: no data found
ORA-06512: at "XXX.P1", line 4
ORA-06512: at line 2

SQL> select count(1) from t;

COUNT(1)
----------
0

So, please be informed 🙂

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