How to generate sessions manually in Oracle

Question

Guys can anybody tell me how I can automatically generate sessions by using some codes rather manually triggering sessions.
See I'm going to implement a multithreading tool by running the tool on different sessions but on a single instant. So I have to run the scripts manually. So I'm unable to run it at the same time. So can anybody tell me how I can generate multiple sessions at the same time & I can run my tool at same time on different sessions(bt in single instant) so that multiple threads(cursors) in multiple sessions can start at same time. So I can check my multithreading tool's performance?

Answer 1

A new feature in Oracle8i called autonomous transactions allows you to make and
save (or roll back) changes within a single PL/SQL block—without affecting the outer or main transaction.
To make a PL/SQL block an autonomous transaction, simply include this statement in the declaration section of the block:
PRAGMA AUTONOMOUS_TRANSACTION;
You can use this statement in any procedure and function and in any non-nested
anonymous block.
Example
create table audit_tab (uname varchar2(30), dt date, msg varchar2(4000));
create or replace trigger emp_trigger
before update of SAL on emp
for each row
declare
     -- this pragma will allow our trigger to commit and
     -- capture an audit trail record. We can then fail
     -- the triggering statement, preventing the update from
     -- occurring
     pragma autonomous_transaction;
     l_cnt     number;
begin
     -- this query just makes sure the empno being updated
     -- is a person who reports to the employee doing the update.
     -- connect by is a nice way to build this hierarchy.
     -- since the where clause is processed after the hierarchy
     -- is built, we can easily use exists on this
     select count(*)
     into l_cnt
     from dual
where exists ( select empno
               from emp
               where empno = :new.empno
               start with mgr =
               (select empno from emp where ename=USER)
               connect by prior empno = mgr );
     -- If the exists returns no rows, we have attempted
     -- to update someone who does not work for us. We
     -- will audit the attempt as well as fail the attempt.
     -- the employee salary will not be updated and we will
     -- have a record of the attempt
     if ( l_cnt = 0 )
     then
     insert into audit_tab values ( user, sysdate,
          'Attempt to update salary of ' ||
          :new.ename || '-' || :new.empno);
     commit;
     raise_application_error( -20001,
          'You have tried to do something you should '||
          'not have and we know it');
     end if;
end;
Trigger created.
Benefits
With autonomous transactions, you can write and save messages in an database log without affecting the main transaction.
You can execute from SQL PL/SQL functions that change the database.
You can write PL/SQL components or cartridges that behave nicely in a distributed
computing environment.
Khurram Siddiqui