ORA-00604 & ORA-30512 CANNOT MODIFY TABLE MORE THAN ONCE IN A TRANSACTION

Question

We have a requirement where two tables should be in sync at any given point
in time with respect to the structure of the tables.
Any change on table/column via ALTER (MODIFY, ADD, RENAME COLUMN, DROP
COLUMN) on the parent table should be replicated to the replica table.
I created a DDL_TRIGGER on the schema and the desired result is achieved but
for the following one scenario for which its failing.
The issue is, if we try to reduce the width of the column (via ALTER ..
MODIFY) it fails with the following error
ORA-00604: error occurred at recursive SQL level 1
ORA-30512: cannot modify DEVTESTF_OIM.REPLICA_ABC more than once in a
transaction
Please follow the steps to reproduce the issue (the issue is across the DB
version checked on 10.2, 11.1 and 11.2 DB version)
-- Step1 Create Parent Table
CREATE TABLE abc (col1 VARCHAR2(10))
-- Step2 Create Replica Table
CREATE TABLE replica_abc (col1 VARCHAR2(10))
-- Step3 Create DDL Trigger
CREATE OR REPLACE TRIGGER ddl_trigger
AFTER ALTER ON SCHEMA
DECLARE
operation VARCHAR2(30);
object_name VARCHAR2(30);
l_sqltext VARCHAR2(100);
i PLS_INTEGER;
l_count NUMBER:=0;
sql_text dbms_standard.ora_name_list_t;
BEGIN
i := dbms_standard.sql_txt(sql_text);
SELECT ora_sysevent, ora_dict_obj_name, UPPER(sql_text(i))
INTO operation, object_name, l_sqltext
FROM dual;
IF ora_dict_obj_name = 'ABC' THEN
l_count := INSTR(l_sqltext,'ADD CONSTRAINT',1,1);
l_count := l_count + INSTR(l_sqltext,'DISABLE',1,1);
l_count := l_count + INSTR(l_sqltext,'DROP CONSTRAINT',1,1);
l_count := l_count + INSTR(l_sqltext,'PRIMARY KEY',1,1);
l_count := l_count + INSTR(l_sqltext,'ADD CHECK',1,1);
IF (l_count = 0) THEN
l_count := INSTR(l_sqltext,'ADD',1,1);
l_count := l_count + INSTR(l_sqltext,'MODIFY',1,1);
l_count := l_count + INSTR(l_sqltext,'DROP COLUMN',1,1);
l_count := l_count + INSTR(l_sqltext,'RENAME
COLUMN',1,1);
IF (l_count >0) THEN
l_sqltext := REPLACE(l_sqltext,'TABLE ABC','TABLE REPLICA_ABC');
execute immediate l_sqltext;
END IF;
END IF;
END IF;
EXCEPTION
WHEN OTHERS THEN
RAISE ;
END;
-- Step 4 Issue the following ALTER command on the Parent table 'ABC'
ALTER TABLE ABC MODIFY COL1 VARCHAR2(9);
will show the following
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-30512: cannot modify DEVTESTF_OIM.REPLICA_ABC more than once in a
transaction
ORA-06512: at line 34
whereas the following commands works fine
ALTER TABLE ABC MODIFY COL1 VARCHAR2(11);
and also the rest of the operations
ALTER TABLE ABC ADD COL2 VARCHAR2(20);
ALTER TABLE ABC RENAME COLUMN COL2 TO COL3;
ALTER TABLE ABC DROP COLUMN COL3;
The issue is while reducing the size of VARCHAR2 columns, while the rest of
option works fine.
Any suggestion or workaround please.

Answer 1

It looks like a bug to me. The failing statement from the SQL trace is
PARSE ERROR #12:len=77 dep=3 uid=0 oct=3 lid=0 tim=1263332549608656 err=30512
select /*+ first_rows */ 1 from "TIM"."REPLICA_ABC" where LENGTHB("COL1") > 9and exception cannot explain it.