On DML operations Locked held on Parent tables.

Question

Hi All,
Am trying to delete records from a table such as
DELETE /*+ index(EVENT_JOURNAL row_ts_idx) */  FROM EVENT_JOURNAL WHERE trunc(ROW_TS)= TO_date('09/05/2012','DD/MM/YYYY');table has function based index on row_ts column
Plan
DELETE STATEMENT  ALL_ROWSCost: 138  Bytes: 502 K  Cardinality: 8 K             
    3 DELETE BENCHMARKDEV.EVENT_JOURNAL        
        2 TABLE ACCESS BY INDEX ROWID TABLE BENCHMARKDEV.EVENT_JOURNAL Cost: 138  Bytes: 502 K  Cardinality: 8 K     
            1 INDEX RANGE SCAN INDEX BENCHMARKDEV.ROW_TS_IDX Cost: 23  Cardinality: 8 K  Above delete operation takes much time to delete 273 rows
I have check that above DML perform getting locked on its parent table. such as
select    OS_USER_NAME os_user,
    PROCESS os_pid,
    ORACLE_USERNAME oracle_user,
    l.SID oracle_id,
    decode(TYPE,
        'MR', 'Media Recovery',
        'RT', 'Redo Thread',
        'UN', 'User Name',
        'TX', 'Transaction',
        'TM', 'DML',
        'UL', 'PL/SQL User Lock',
        'DX', 'Distributed Xaction',
        'CF', 'Control File',
        'IS', 'Instance State',
        'FS', 'File Set',
        'IR', 'Instance Recovery',
        'ST', 'Disk Space Transaction',
        'TS', 'Temp Segment',
        'IV', 'Library Cache Invalidation',
        'LS', 'Log Start or Switch',
        'RW', 'Row Wait',
        'SQ', 'Sequence Number',
        'TE', 'Extend Table',
        'TT', 'Temp Table', type) lock_type,
    decode(LMODE,
        0, 'None',
        1, 'Null',
        2, 'Row-S (SS)',
        3, 'Row-X (SX)',
        4, 'Share',
        5, 'S/Row-X (SSX)',
        6, 'Exclusive', lmode) lock_held,
    decode(REQUEST,
        0, 'None',
        1, 'Null',
        2, 'Row-S (SS)',
        3, 'Row-X (SX)',
        4, 'Share',
        5, 'S/Row-X (SSX)',
        6, 'Exclusive', request) lock_requested,
    decode(BLOCK,
        0, 'Not Blocking',
        1, 'Blocking',
        2, 'Global', block) status,
    OWNER,
    OBJECT_NAME
from    v$locked_object lo,
    dba_objects do,
    v$lock l
where     lo.OBJECT_ID = do.OBJECT_ID
AND     l.SID = lo.SESSION_ID
oracle     6624     BENCHMARKDEV     216     DML     Row-X (SX)     None     Not Blocking     BENCHMARKDEV     BUSINESS_UNIT
oracle     6624     BENCHMARKDEV     216     DML     Row-X (SX)     None     Not Blocking     BENCHMARKDEV     BUSINESS_UNIT
oracle     6624     BENCHMARKDEV     216     DML     Row-X (SX)     None     Not Blocking     BENCHMARKDEV     BUSINESS_UNIT
oracle     6624     BENCHMARKDEV     216     DML     Row-X (SX)     None     Not Blocking     BENCHMARKDEV     BUSINESS_UNIT
oracle     6624     BENCHMARKDEV     216     DML     Row-X (SX)     None     Not Blocking     BENCHMARKDEV     BUSINESS_UNIT
oracle     6624     BENCHMARKDEV     216     DML     Row-X (SX)     None     Not Blocking     BENCHMARKDEV     BUSINESS_UNIT
oracle     6624     BENCHMARKDEV     216     DML     Row-X (SX)     None     Not Blocking     BENCHMARKDEV     BUSINESS_UNIT
oracle     6624     BENCHMARKDEV     216     DML     Row-X (SX)     None     Not Blocking     BENCHMARKDEV     BUSINESS_UNIT
oracle     6624     BENCHMARKDEV     216     DML     Row-X (SX)     None     Not Blocking     BENCHMARKDEV     BUSINESS_UNIT
oracle     6624     BENCHMARKDEV     216     Transaction     Exclusive     None     Not Blocking     BENCHMARKDEV     BUSINESS_UNIT
oracle     6624     BENCHMARKDEV     216     DML     Row-X (SX)     None     Not Blocking     BENCHMARKDEV     BUSINESS_UNITI don't know on what basis parent tables are get locked?
Please help me out to resolve..
Thanks & Regards
Sami
Edited by: Sami on May 16, 2012 3:14 PM
Edited by: Sami on May 16, 2012 3:15 PM

Answer 1

Hi Sami,
Your dont event need Function Based Index on ROW_TS. A normal B*Tree index on ROW_TS will do the trick and also reduce the time for index sorting.
DELETE FROM EVENT_JOURNAL WHERE ROW_TS >= TO_date('09/05/2012','DD/MM/YYYY') AND ROW_TS < TO_date('10/05/2012','DD/MM/YYYY');
{code}
{code}
Above delete operation takes much time to delete 273 rows
{code}
# Is EVENT_JOURNAL parent table and has foreign key references from other tables ?
# How many records are there in EVENT_JOURNAL ?
# Check data dictionary view - DBA_WAITERS to see waiting/holding session