How to enable DML logging

DML logging can be used as a workaround if you have a large number of rows to process, and you expect that some of these will fail to be inserted correctly due to data quality problems. In other words, some rows may violate one or more constraints on the receiving table.

Here is a short demonstration that I have recently tested as a workaround for a client.

I have a table called MYTABLE, which looks like this:

 Name                   Null?    Type
 --------------------- -------- -------------------
 ORDER_ID                        NOT NULL NUMBER
 ORG_ORDERID                     NUMBER
 VALUE_ID_TYPE                   VARCHAR2(20)
 COL_PREFIX                      VARCHAR2(80)
 COL_NAME                        VARCHAR2(500)
 COL_SUFFIX                      VARCHAR2(20)

There is a unique constraint on the table:

--create the index
CREATE UNIQUE INDEX C_COL_UIX ON MYTABLE
(ORG_ORDERID, COL_PREFIX, COL_NAME, COL_SUFFIX)
TABLESPACE USERS;

-- create the constraint, using index created above
ALTER TABLE MYTABLE ADD (
  CONSTRAINT C_COL_CONS
  UNIQUE (ORG_ORDERID, COL_PREFIX, COL_NAME, COL_SUFFIX)
  USING INDEX C_COL_UIX);

The actual DML logging is performed by adding the statement

LOG ERRORS INTO error_table ('INSERT') REJECT LIMIT UNLIMITED;

at the end of the INSERT statement.

Before we can do this we need to create the error log table:

BEGIN
  DBMS_ERRLOG.create_error_log (dml_table_name => 'MYTABLE');
END;
/

The statement above will create a table called ERR$_MYTABLE, where rejected rows will be inserted into.

For this test, I will now verify that the values I intend to use, actually exist in the table:

select count(*)
from mytable
where org_orderid = 122
and col_prefix = 'A'
and col_name = 'B'
and col_suffix = 'X'
;

  COUNT(*)
----------
         1

Any attempt to insert a row into the table with the same values as in the select statement above (122, A, B, X), will violate constraint C_COL_CONS, and logged in the table ERR$_MYTABLE.

Let's execute an INSERT statement that will violate the constraint:

INSERT
INTO mytable (order_id, col_prefix, col_name, col_suffix, col_type)
VALUES(122, 'A', 'B', 'X', 'D')
LOG ERRORS INTO ERR$_MYTABLE ('INSERT') REJECT LIMIT UNLIMITED;

As expected, I get the following error:

ORA-00001: unique constraint (C_COL_CONS) violated

Let's check the log table:

SELECT * FROM ERR$_MYTABLE;

ORA_ERR_NUMBER$	ORA_ERR_MESG$	ORA_ERR_ROWID$	ORA_ERR_OPTYP$	ORA_ERR_TAG$	ORDER_ID	ORG_ORDERID	VALUE_ID_TYPE	COL_PREFIX	COL_NAME	COL_SUFFIX
1	ORA-00001: unique constraint (C_COL_CONS; violated		I	INSERT	2850841	122	D	A	B	X

If you execute a batchjob with thousands of rows, the offending rows will be caught so they can be corrected later. The non-offending rows will be neatly inserted where they belong.

How to use ROWTYPE to fetch entire rows for insert into an interim table

Here is how I used a PL/SQL record to insert rows from a table into an interim table, using parallel slaves and direct path:

alter session force parallel dml;
alter session force parallel query;

DECLARE
  --declare a table-based record for the table "document"
  v_document_rec document%ROWTYPE;

  CURSOR document_cur IS
    SELECT *
    FROM document
    WHERE trunc(created_date) between TO_DATE('01.01.2017','dd.mm.yyyy') AND to_date(to_char(SYSDATE,'dd.mm.yyyy'))
    FETCH FIRST 100000 ROWS ONLY;

   -- declare a cursor-based record
   v_document_rec document_cur%ROWTYPE;

BEGIN
   OPEN document_cur;
   LOOP
   -- fetch the content of the cursor into the record
   FETCH document_cur into v_document_rec;
   EXIT WHEN document_cur%NOTFOUND;
   INSERT /*+ APPEND PARALLEL 8 */ INTO document_interim VALUES( v_document_rec.ID,
                                                 v_document_rec.document_id,
                                                 v_document_rec.document_name,
                                                 v_document_rec.created_date,
                                                 v_document_rec.security_level,
                                                 v_document_rec.content );
   END LOOP;
   COMMIT;
   CLOSE document_cur;
END;
/

Insert As Select statements

The syntax for an Insert As Select Statement would be:

INSERT INTO MY_INTERIM_TABLE (E_ID, ENAME,CREATED_DT, REVISION, FISCALYEAR, FPERIOD, PHONENBR)
                       SELECT E_ID, ENAME,CREATED_DT, REVISION, FISCALYEAR, TO_DATE(FPERIOD,'YYYY-MM'), PHONENBR
                       FROM   MY_ORIGINAL_TABLE
                       FETCH FIRST 5 ROWS ONLY;

The FETCH FIRST num ROWS ONLY is a convenient way to limit the number of rows when you are setting up tables for test purposes.

Example on how to use WITH CHECK OPTION in an INSERT statement

The table "ALBUM" has the following columns:

Name         Null     Type                        
------------ -------- --------------------------- 
ALBUM_ID     NOT NULL NUMBER                      
ALBUM_TITLE  NOT NULL VARCHAR2(50 CHAR)           
ARTIST_ID             NUMBER                      
RELEASE_DATE          TIMESTAMP(6) WITH TIME ZONE 
GENRE                 VARCHAR2(30)                
NUM_SOLD              NUMBER                      
COLLECTION            CHAR(1)        

Extract all albums by the band Kiss:

SELECT ARTIST_ID, ALBUM_TITLE
 FROM ALBUM
 WHERE ARTIST_ID = (SELECT ARTIST_ID FROM ARTIST WHERE ARTIST_NAME='Kiss');

 ARTIST_ID ALBUM_TITLE                                      
---------- ------------
        13 Dynasty            

Add another entry to the "ALBUM" table:

SQL> INSERT INTO
  2  (
  3   SELECT album_id, album_title, artist_id,release_date, genre, num_sold
  4   FROM album
  5   WHERE num_sold BETWEEN 10000 AND 50000
  6   AND artist_id=13 WITH CHECK OPTION
  7   )
  8   VALUES( album_seq.nextval, '&album_title', &artist_id, to_date('&release_date','dd.mm.yyyy'), 'HARD ROCK', 20000 );
Enter value for album_title: Love Gun
Enter value for artist_id: 13
Enter value for release_date: 30.06.1977
old   8:  VALUES( album_seq.nextval, '&album_title', &artist_id, to_date('&release_date','dd.mm.yyyy'), 'HARD ROCK', 20000 )
new   8:  VALUES( album_seq.nextval, 'Love Gun', 13, to_date('30.06.1977','dd.mm.yyyy'), 'HARD ROCK', 20000 )

1 row inserted.

COMMIT;

Run the SELECT above once more to confirm the row has been entred:

ARTIST_ID ALBUM_TITLE                                      
---------- -----------------------
        13 Love Gun                             
        13 Dynasty            

Any attempt to enter values that is not included in the subquery would cause an

ORA-01402: view WITH CHECK OPTION where-clause violation

to be raised.
For example, try entering 15 as the artist_id:

Enter value for album_title: Creatures of the Night
Enter value for artist_id: 15
Enter value for release_date: 13.10.1982
old   8:  VALUES( album_seq.nextval, '&album_title', &artist_id, to_date('&release_date','dd.mm.yyyy'), 'HARD ROCK', 20000 )
new   8:  VALUES( album_seq.nextval, 'Creatures of the Night', 15, to_date('13.10.1982','dd.mm.yyyy'), 'HARD ROCK', 20000 )
 VALUES( album_seq.nextval, 'Creatures of the Night', 15, to_date('13.10.1982','dd.mm.yyyy'), 'HARD ROCK', 20000 )
         *
ERROR at line 8:
ORA-01402: view WITH CHECK OPTION where-clause violation

Note that the subquery, when used in an INSERT statement as above, replaces the table name, as well as the column list.

Source: Oracle documentation

How to add a logfile group and a logfile member - syntax

alter database add logfile group 2
(
'/u01/app/oracle/flash_recovery_area/mydb/onlinelog/redo02a.log',
'/u01/app/oracle/oradata/mydb/onlinelog/redo02b.log'
) size 50M;

Remember, if you have just recently dropped the redo log members, they are still present physically on disk.
If you'd like to reuse the log file member names, and to avoid

ORA-00301: error in adding log file /u03/oradata/arutvt/redo03.log - file cannot be created,

add the REUSE keyword at the end of the statement:

alter database add logfile group 3 ('/u03/oradata/mydb/redo03.log') size 1024M REUSE;

To add another member to an already existing group:

ALTER DATABASE ADD LOGFILE MEMBER '/u03/oradata/mydb/redo03.log' TO GROUP 3;

If the redo log file member is already present on disk, use reuse:

ALTER DATABASE ADD LOGFILE MEMBER '/u03/oradata/mydb/redo3b.log' REUSE TO GROUP 3;

If you do not specifically say which log group number you want to create, Oracle will take add another group based on the largest log file group number in v$logfile. So if I have 3 groups already, and execute

alter database add logfile '/rdodata/mydb/redo04.log' size 2048M;

It will create group number 4 for you, even if you do not explicitly say so:

SYS@cdb>SQL>@redo

    GROUP# MEMBER                                                     MB ARC STATUS            SEQUENCE#
---------- -------------------------------------------------- ---------- --- ---------------- ----------
         1 /rdodata/mydbredo01.log                              2048 YES INACTIVE                220
         2 /rdodata/mydb/redo02.log                             2048 YES INACTIVE                221
         3 /rdodata/mydb/redo03.log                             2048 NO  CURRENT                 222
         4 /rdodata/mydb/redo04.log                             2048 YES UNUSED                    0

Documentation for Oracle 19c is found here

An easy way to find DML locks

The view DBA_DML_LOCKS is a convenient view to use if you want to identify locks caused by uncommited DML statements.

Consider the following simple example:

INSERT INTO FAMILY_TREE
(PERSON_ID, FULL_NAME, GENDER, CITIZENSHIP, COUNTRY_OF_RESIDENCE)
VALUES
(5, 'Arne Kåsa', 'M', 'Norwegian', 'Sweden');

-- Do not commit --

Logged in as a privileged user from another session, execute:

SELECT * FROM DBA_DML_LOCKS WHERE OWNER = 'VEGARDK';

SESSION_ID	OWNER	NAME	MODE_HELD	MODE_REQUESTED	LAST_CONVERT	BLOCKING_OTHERS
362	VEGARDK	FAMILY_TREE	Row-X (SX)	None	39	Not Blocking

COMMIT;

SELECT * FROM DBA_DML_LOCKS WHERE OWNER = 'VEGARDK';

No rows returned.