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

SQL*Plus: Release 11.2.0.2.0 Production on Sßb Feb 08 00:10:51 2020

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Connected to:
Oracle Database 11g Express Edition Release 11.2.0.2.0 - 64bit Production

SQL> create table test(nombre varchar2(30), numero number);

Table created.

SQL> insert /*+ append */ into test select table_name,num_rows from user_tables;

833 rows created.

SQL> select count(*) from test;
select count(*) from test
                     *
ERROR at line 1:
ORA-12838: cannot read/modify an object after modifying it in parallel


SQL> commit;

Commit complete.

SQL> select count(*) from test;

  COUNT(*)
----------
        833

SQL>