Search notes:

ORA-12838: cannot read/modify an object after modifying it in parallel

Make sure our session is enabled for parallel DML:

select pdml_status from v$session where sid = sys_context('userenv', 'sid');
alter session enable parallel dml;

Create a table for the result:

create table tq84_objs (own varchar2(128), nam varchar2(128));

Insert data with parallel execution:

insert /*+ parallel */ into tq84_objs
select
   owner,
   object_name
from
   dba_objects;

Verify if statement was executed in parallel:

select * from v$pq_sesstat order by statistic;

Following statement throws ORA-12838: cannot read/modify an object after modifying it in parallel:

delete from tq84_objs where own = 'SYS';

We have to commit the transaction in order to further modify data in the table:

commit;
delete from tq84_objs where own = 'SYS';

See also