The automatic indexing feature automates index management tasks, such as creating,
rebuilding, and dropping indexes in an Oracle database based on changes in the application
workload.

This feature improves database performance by managing indexes automatically in an Oracle database.

Set the ADG_REDIRECT_DML initialization parameter to TRUE.

ALTER SESSION ENABLE ADG_REDIRECT_DML;

[ora19@whf307 ~]$ sqlplus  system/oracle

SQL*Plus: Release 19.0.0.0.0 - Production on Sat Mar 9 00:45:45 2019
Version 19.2.0.0.0

Copyright (c) 1982, 2018, Oracle.  All rights reserved.


Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.2.0.0.0

SQL> alter session set container=&pdb;
Enter value for pdb: pdbll
old   1: alter session set container=&pdb
new   1: alter session set container=pdborcl

Session altered.

SQL> select open_mode,database_role from v$database;

OPEN_MODE            DATABASE_ROLE
-------------------- ----------------
READ ONLY WITH APPLY PHYSICAL STANDBY

SQL> select * from t1;

        ID
----------
         1
         2
         2

SQL> insert into t1 values(3);

1 row created.

SQL> commit;

Commit complete.

SQL> select  * from t1;

        ID
----------
         1
         2
         2
         3

SQL> show parameter ADG_REDIRECT_DML

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
adg_redirect_dml                     boolean     TRUE
SQL> 

SQL> select * from sa.t1 where id=1;

        ID NAME               C1
---------- ---------- ----------
         1 x                   1
         1 yy                  1
         1 x                   2

SQL> update sa.t1 set c1=1 where id=1;
update sa.t1 set c1=1 where id=1
          *
ERROR at line 1:
ORA-16397: statement redirection from Oracle Active Data Guard standby database to primary database failed

[ora19@whf307 ~]$ oerr ora 16397
16397, 00000, "statement redirection from Oracle Active Data Guard standby database to primary database failed"
// *Cause:  The statement redirection failed because of one of the following reasons:
//          1. The primary database connect string was not established.
//          2. The primary database could not be reached.
//          3. The undo-mode or incarnation were not the same.
//          4. The current user and logged-in user were not the same.
//          5. Redirecting CREATE TABLE AS SELECT (CTAS) of the global temporary
//             table was not supported.
//          6. Redirecting PL/SQL execution having bind variable was not supported.
// *Action: Run the statement after fixing the condition that caused the failure.