Delete Query takes more time

Question

Hi,
My database in 10g(10.2.0.4), I fire delete query which deletes 5 Lacs records from the table but it is taking more time to delete.
My table and indexes on that table in Nologging mode, Database in Archive Log Mode.
Can you please help to minize the time?
Execution Plan
0 DELETE STATEMENT Optimizer=ALL_ROWS (Cost=2 Card=1 Bytes=62)
1 0 DELETE OF 'CORP_MESSAGEQUEUE'
2 1 INDEX (RANGE SCAN) OF 'INDEX_CORP_MESSAGEQUEUE_PROC' (IN
DEX) (Cost=2 Card=1 Bytes=62)
Statistics
754 recursive calls
635137 db block gets
4773 consistent gets
181579 physical reads
268073944 redo size
630 bytes sent via SQL*Net to client
608 bytes received via SQL*Net from client
3 SQL*Net roundtrips to/from client
1 sorts (memory)
4 sorts (disk)
483328 rows processed
Anand

Answer 1

Even if the table is in nologing mode there will be redo generated for the DML. It is clear from your statistics that redo is being generated for the delete. Loging is only effective for few of the operations as given bellow. I think there is no issue with the query the redo and undo generation is taking time. Just tune your configuration like.
No redo log files.
size of redo log.
Undo tablespace size.
undo retentation.
Pga_aggrigate_target.
temporary tablespace sizing.
754 recursive calls
635137 db block gets
4773 consistent gets
181579 physical reads
**268073944 redo size**
630 bytes sent via SQL*Net to client
608 bytes received via SQL*Net from client
3 SQL*Net roundtrips to/from client
1 sorts (memory)
4 sorts (disk)
483328 rows processed
NOLOGGING: Oracle will generate a minimal number of redo log entries in order to protect the data dictionary, and the operation will probably run faster. Logging can be disabled at the table level or the tablespace level.
If it is done at the tablespace level then we create indexes or tables in this tablespace; they will be in NOLOGGING mode.
A table or an index can be created with NOLOGGING mode or it can be altered using ALTER TABLE/INDEX NOLOGGING.
NOLOGGING is active in the following situations and while running one of the following commands but not after that.
- DIRECT LOAD (SQL*Loader)
- DIRECT LOAD INSERT (using APPEND hint)
- CREATE TABLE ... AS SELECT
- CREATE INDEX
- ALTER TABLE MOVE
- ALTER TABLE ... MOVE PARTITION
- ALTER TABLE ... SPLIT PARTITION
- ALTER TABLE ... ADD PARTITION (if HASH partition)
- ALTER TABLE ... MERGE PARTITION
- ALTER TABLE ... MODIFY PARTITION, ADD SUBPARTITON, COALESCE SUBPARTITON, REBUILD UNUSABLE INDEXES
- ALTER INDEX ... SPLIT PARTITION
- ALTER INDEX ... REBUILD
- ALTER INDEX ... REBUILD PARTITION
Logging is stopped only while one of the commands above is running.
So if a user runs this:
ALTER INDEX new_index NOLOGGING.
The actual rebuild of the index does not generate redo (all data dictionary changes associated with the rebuild will do) but after that any DML on the index will generate redo this includes direct load insert on the table which the index belongs to.
All the following statements will generate redo despite the fact the table is in NOLOGGING mode:
- INSERT INTO new_table_nolog_test ...,
- UPDATE new_table_nolog_test SET ...,
- DELETE FROM new_table_nolog_test ..
The following will not generate redo (except from dictionary changes and indexes):
- INSERT /*APPEND/ ...
- ALTER TABLE new_table_nolog_test MOVE ...
- ALTER TABLE new_table_nolog_test MOVE PARTITION ...
practicle example:
SQL> select value OLD_VALUE
from v$mystat, v$statname
where v$mystat.statistic# = v$statname.statistic#
and v$statname.name = 'redo size'; 2 3 4
OLD_VALUE
0
SQL> /
OLD_VALUE
0
SQL>
SQL> create table T_NOLOG nologging as select * from all_objects;
Table created.
SQL> select (value - &OLD_VALUE) OLD_VALUE
from v$mystat, v$statname
where v$mystat.statistic# = v$statname.statistic#
and v$statname.name = 'redo size'; 2 3 4
Enter value for old_value: 0
old 1: select (value - &OLD_VALUE) OLD_VALUE
new 1: select (value - 0) OLD_VALUE
OLD_VALUE
91848
SQL> delete from T_NOLOG ;
106229 rows deleted.
SQL> select (value - &OLD_VALUE) OLD_VALUE
from v$mystat, v$statname
where v$mystat.statistic# = v$statname.statistic#
and v$statname.name = 'redo size'; 2 3 4
Enter value for old_value: 91848
old 1: select (value - &OLD_VALUE) OLD_VALUE
new 1: select (value - 91848) OLD_VALUE
OLD_VALUE
39389988
SQL>