ORA-08177: can't serialize access for this transaction

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Reference

My Oracle Support Note : Insert Into Table Fails With ORA-08177 (Doc ID 160593.1)

Error Explanation

Symptoms:

•symptom: Insert into table fails

•symptom: ORA-08177: can't serialize access for this transaction

•symptom: transaction isolation level is serializable

•symptom: The table has index definitions

•symptom: Several transaction insert data into same table

•cause: The problem manifest itself when there are indexes on the table   
 to which the rows are being inserted.  Without any indexes the problem will not reproduce     

Cause:
Concurrent inserts into a table with index using serializable transactions could lead to an index split that the transaction tries to re-read and cause an error ORA-08177

Reproduce the error

First, as use robla, create the test objects:

SQL> create table emp2 as select * from emp where rownum < 1;

Table created.

SQL> create index emp2_indx on emp2(empno); 

Index created.

In two separate SQL sessions, as user robla, enter the following commands, i.e. type each individual command on one session followed immediately on the other session. (Do not connect as sys as you can't set the transaction isolation level as sys):

-- Session 1:
SQL_01> set transaction isolation level serializable;

Transaction set.

SQL> insert into emp2 select * from emp;

14 rows created.
-- Sesssion 2:
SQL_02> set transaction isolation level serializable;

SQL> insert into emp2 select * from emp;

14 rows created.
-- Session 1:
SQL_01> set transaction isolation level serializable;

Transaction set.

SQL> insert into emp2 select * from emp;

ERROR at line 1:
ORA-08177: can't serialize access for this transaction