Minimize full table scan

Dear all,
I have a query involving some equal and outer joins and I have created the required indexes which are used for comparison. However, when I use the explain plan, I found the execution plan choose full table scan rather than scanning the index.
When I try the query in test environment, it goes through the indexes and responses quickly. The amount and nature of data are more or less the same.
Any idea?

It is not because you create an index that Oracle will use that index. It depends on the optimiser mode and on the number of expected rows. If you use the cost-based-optimiser and oracle thinks that the query returns more than 4% of the rows in the table, it uses full tablescan instead of indexscan. If you do not agree with this way, use hints or let oracle analyse your tables.
null

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    Edited by: user11117178 on Jul 30, 2009 6:23 AM
    Edited by: user11117178 on Jul 30, 2009 6:24 AM

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    PLAN_TABLE_OUTPUT
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    | Id  | Operation                     | Name                    | Rows  | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
    |   0 | SELECT STATEMENT              |                         |   324K|    33M|  3138   (5)| 00:00:38 |       |       |
    |*  1 |  HASH JOIN                    |                         |   324K|    33M|  3138   (5)| 00:00:38 |       |       |
    |   2 |   BITMAP CONVERSION TO ROWIDS |                         |     3 |     9 |     1   (0)| 00:00:01 |       |       |
    |*  3 |    BITMAP INDEX FAST FULL SCAN| IDX_PS2_ACTION_TYPES    |       |       |            |          |       |       |
    |   4 |   PARTITION RANGE ITERATOR    |                         |   866K|    87M|  3121   (4)| 00:00:38 |   154 |   158 |
    |   5 |    TABLE ACCESS FULL          | PS2_FS_TRANSACTION_FACT |   866K|    87M|  3121   (4)| 00:00:38 |   154 |   158 |
    Predicate Information (identified by operation id):
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    'L*', 'Was showing unbalanced journal entry by account category',
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    'N*', 'Journal produced error during intercompany balance processing',
    'O', 'Unable to convert amounts into reporting currency',
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    'Q*', 'Was showing untaxed journal entry',
    'R', 'Showing unbalanced encumbrance entry without reserve account',
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    SELECT STATEMENT
    SORT GROUP BY
    VIEW SYS
    SORT GROUP BY
    NESTED LOOPS OUTER
    NESTED LOOPS OUTER
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS OUTER
    NESTED LOOPS OUTER
    NESTED LOOPS
    NESTED LOOPS OUTER
    NESTED LOOPS OUTER
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS
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    INDEX RANGE SCAN GL.GL_CODE_COMBINATIONS_N1
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    INDEX UNIQUE SCAN GL.GL_JE_HEADERS_U1
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    INDEX UNIQUE SCAN GL.GL_DAILY_CONVERSION_TYPES_U1
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    INDEX UNIQUE SCAN GL.GL_JE_SOURCES_TL_U1
    INDEX UNIQUE SCAN GL.GL_JE_CATEGORIES_TL_U1
    INDEX UNIQUE SCAN GL.GL_JE_HEADERS_U1
    INDEX UNIQUE SCAN GL.GL_JE_HEADERS_U1
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    INDEX UNIQUE SCAN GL.GL_SETS_OF_BOOKS_U2
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    NESTED LOOPS OUTER
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS OUTER
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS
    NESTED LOOPS
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    NESTED LOOPS
    NESTED LOOPS OUTER
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    INDEX UNIQUE SCAN GL.GL_JE_HEADERS_U1
    INDEX UNIQUE SCAN GL.GL_JE_HEADERS_U1
    INDEX UNIQUE SCAN GL.GL_JE_HEADERS_U1
    _________________________________

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    AND version_number = 3;
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       1    0   SORT (AGGREGATE)
       2    1     TABLE ACCESS (FULL) OF 'MYTABLE' (TABLE)
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              0  db block gets
             29  consistent gets
              0  physical reads
              0  redo size
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            276  bytes received via SQL*Net from client
              2  SQL*Net roundtrips to/from client
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              0  sorts (disk)
              1  rows processed
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              0  redo size
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  • How can i make the optimiser to skip this full table scan ??

    Hi,
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    ,INITCAP (lu.full_name) AS logged_name
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    | 1 | UNION-ALL | | | | |
    | 2 | NESTED LOOPS OUTER | | 2103 | 3665K| 37683 |
    | 3 | VIEW | | 2103 | 3616K| 35580 |
    | 4 | NESTED LOOPS OUTER | | 2103 | 823K| 35580 |
    | 5 | NESTED LOOPS OUTER | | 2103 | 774K| 33477 |
    | 6 | NESTED LOOPS OUTER | | 2103 | 685K| 31374 |
    | 7 | NESTED LOOPS | | 2103 | 636K| 29271 |
    | 8 | NESTED LOOPS | | 2103 | 603K| 27168 |
    | 9 | NESTED LOOPS OUTER | | 2103 | 558K| 25065 |
    | 10 | NESTED LOOPS OUTER | | 2103 | 515K| 22962 |
    | 11 | NESTED LOOPS | | 2103 | 472K| 20859 |
    | 12 | NESTED LOOPS | | 2103 | 429K| 18756 |
    | 13 | NESTED LOOPS OUTER | | 4826 | 890K| 13930 |
    | 14 | NESTED LOOPS OUTER | | 4826 | 848K| 9104 |
    | 15 | NESTED LOOPS | | 4826 | 754K| 4278 |
    |* 16 | TABLE ACCESS FULL | COM_RPTORGANIZATION | 75 | 1050 | 3 |
    | 17 | TABLE ACCESS BY INDEX ROWID | VHD_CALLDESK | 64 | 9344 | 57 |
    |* 18 | INDEX RANGE SCAN | VHD_CALLDSK_ORGID | 2476 | | 7 |
    | 19 | VIEW PUSHED PREDICATE | | 1 | 20 | 1 |
    |* 20 | FILTER | | | | |
    | 21 | TABLE ACCESS BY INDEX ROWID | VHD_CALLDESK_HISTORY | 1 | 20 | 2 |
    |* 22 | INDEX RANGE SCAN | VHD_CALLDSK_HIST_CALLID_IDX | 1 | | 1 |
    |* 23 | FILTER | | | | |
    | 24 | SORT GROUP BY NOSORT | | 1 | 12 | 2 |
    | 25 | TABLE ACCESS BY INDEX ROWID | VHD_CALLDESK_HISTORY | 1 | 12 | 2 |
    |* 26 | INDEX RANGE SCAN | VHD_CALLDSK_HIST_CALLID_IDX | 1 | | 1 |
    | 27 | TABLE ACCESS BY INDEX ROWID | VHD_CALLMODE | 1 | 9 | 1 |
    |* 28 | INDEX UNIQUE SCAN | VHD_CALLMOD_MODID_PK | 1 | | |
    | 29 | TABLE ACCESS BY INDEX ROWID | VHD_APPLICATIONS | 1 | 20 | 1 |
    |* 30 | INDEX UNIQUE SCAN | VHD_APPL_APPLID_PK | 1 | | |
    | 31 | TABLE ACCESS BY INDEX ROWID | VHD_CALLTYPES | 1 | 21 | 1 |
    |* 32 | INDEX UNIQUE SCAN | VHD_CALLTYP_ID_PK | 1 | | |
    | 33 | TABLE ACCESS BY INDEX ROWID | VHD_TEAMS | 1 | 21 | 1 |
    |* 34 | INDEX UNIQUE SCAN | VHD_TEAMID_PK | 1 | | |
    | 35 | TABLE ACCESS BY INDEX ROWID | VHD_ENVIRONMENT | 1 | 21 | 1 |
    |* 36 | INDEX UNIQUE SCAN | VHD_ENV_APLENVID_PK | 1 | | |
    | 37 | TABLE ACCESS BY INDEX ROWID | VHD_MODULES | 1 | 22 | 1 |
    |* 38 | INDEX UNIQUE SCAN | VHD_MOD_APLMOD_ID_PK | 1 | | |
    | 39 | TABLE ACCESS BY INDEX ROWID | COM_ORGANIZATION | 1 | 16 | 1 |
    |* 40 | INDEX UNIQUE SCAN | COM_ORG_PK | 1 | | |
    | 41 | TABLE ACCESS BY INDEX ROWID | LCC_USERINFO_DETAILS | 1 | 24 |
    |* 42 | INDEX UNIQUE SCAN | LCCUSERINFOIND | 1 | | |
    | 43 | TABLE ACCESS BY INDEX ROWID | LCC_USERINFO_DETAILS | 1 | 43 |
    |* 44 | INDEX UNIQUE SCAN | LCCUSERINFOIND | 1 | | |
    | 45 | TABLE ACCESS BY INDEX ROWID | LCC_USERINFO_DETAILS | 1 | 24 | 1
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    | 47 | TABLE ACCESS BY INDEX ROWID | LCC_USERINFO_DETAILS | 1 | 24 | 1
    |* 48 | INDEX UNIQUE SCAN | LCCUSERINFOIND | 1 | | |
    | 49 | NESTED LOOPS OUTER | | 1 | 1785 | 13 |
    | 50 | VIEW | | 1 | 1761 | 12 |
    | 51 | NESTED LOOPS OUTER | | 1 | 1656 | 12 |
    | 52 | NESTED LOOPS OUTER | | 1 | 1632 | 11 |
    | 53 | NESTED LOOPS OUTER | | 1 | 1608 | 10 |
    | 54 | NESTED LOOPS | | 1 | 1565 | 9 |
    | 55 | NESTED LOOPS | | 1 | 1549 | 9 |
    | 56 | NESTED LOOPS | | 1 | 1535 | 9 |
    | 57 | NESTED LOOPS OUTER | | 1 | 1513 | 8 |
    | 58 | NESTED LOOPS OUTER | | 1 | 1492 | 7 |
    | 59 | NESTED LOOPS | | 1 | 1471 | 6 |
    | 60 | NESTED LOOPS | | 1 | 1450 | 5 |
    | 61 | NESTED LOOPS OUTER | | 1 | 1430 | 4 |
    | 62 | NESTED LOOPS OUTER | | 1 | 1421 | 3 |
    | 63 | TABLE ACCESS FULL | VHD_CALLDESK_ARCHIVE | 1 | 1401 | 2 |
    | 64 | VIEW PUSHED PREDICATE | | 1 | 20 | 1 |
    |* 65 | FILTER | | | | |
    | 66 | TABLE ACCESS BY INDEX ROWID | VHD_CALLDESK_HISTORY | 1 | 20 | 2 |
    |* 67 | INDEX RANGE SCAN | VHD_CALLDSK_HIST_CALLID_IDX | 1 | | 1 |
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    | 69 | SORT GROUP BY NOSORT | | 1 | 12 | 2 |
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    |* 71 | INDEX RANGE SCAN | VHD_CALLDSK_HIST_CALLID_IDX | 1 | | 1 |
    | 72 | TABLE ACCESS BY INDEX ROWID | VHD_CALLMODE | 1 | 9 | 1 |
    |* 73 | INDEX UNIQUE SCAN | VHD_CALLMOD_MODID_PK | 1 | | |
    | 74 | TABLE ACCESS BY INDEX ROWID | VHD_APPLICATIONS | 1 | 20 | 1 |
    |* 75 | INDEX UNIQUE SCAN | VHD_APPL_APPLID_PK | 1 | | |
    | 76 | TABLE ACCESS BY INDEX ROWID | VHD_CALLTYPES | 1 | 21 | 1 |
    |* 77 | INDEX UNIQUE SCAN | VHD_CALLTYP_ID_PK | 1 | | |
    | 78 | TABLE ACCESS BY INDEX ROWID | VHD_TEAMS | 1 | 21 | 1 |
    |* 79 | INDEX UNIQUE SCAN | VHD_TEAMID_PK | 1 | | |
    | 80 | TABLE ACCESS BY INDEX ROWID | VHD_ENVIRONMENT | 1 | 21 | 1 |
    |* 81 | INDEX UNIQUE SCAN | VHD_ENV_APLENVID_PK | 1 | | |
    | 82 | TABLE ACCESS BY INDEX ROWID | VHD_MODULES | 1 | 22 | 1 |
    |* 83 | INDEX UNIQUE SCAN | VHD_MOD_APLMOD_ID_PK | 1 | | |
    | 84 | TABLE ACCESS BY INDEX ROWID | COM_RPTORGANIZATION | 1 | 14 | |
    |* 85 | INDEX UNIQUE SCAN | COM_RPTORG_PK | 1 | | |
    | 86 | TABLE ACCESS BY INDEX ROWID | COM_ORGANIZATION | 1 | 16 | |
    |* 87 | INDEX UNIQUE SCAN | COM_ORG_PK | 1 | | |
    | 88 | TABLE ACCESS BY INDEX ROWID | LCC_USERINFO_DETAILS | 1 | 43 |
    |* 89 | INDEX UNIQUE SCAN | LCCUSERINFOIND | 1 | | |
    | 90 | TABLE ACCESS BY INDEX ROWID | LCC_USERINFO_DETAILS | 1 | 24 |
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    | 92 | TABLE ACCESS BY INDEX ROWID | LCC_USERINFO_DETAILS | 1 | 24 | 1
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    | 94 | TABLE ACCESS BY INDEX ROWID | LCC_USERINFO_DETAILS | 1 | 24 | 1
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    75 - access("D"."APPL_ID"="SYS_ALIAS_1"."APPL_ID")
    77 - access("F"."CALL_TYPE_ID"="SYS_ALIAS_1"."CALL_TYPE_ID")
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        AND a.appl_id          = e.appl_id
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    AND ac2.assignment_action_id = int.locking_action_id
    AND pa3.payroll_action_id = ac2.payroll_action_id
    AND pa3.action_type IN ('P', 'U')
    AND NOT EXISTS
    SELECT /*+ PARALLEL*/
    NULL
    FROM per_all_assignments_f as3
    , pay_assignment_actions ac3
    WHERE :b4 = 'N'
    AND ac3.payroll_action_id = pa2.payroll_action_id
    AND ac3.action_status NOT IN ('C', 'S')
    AND as3.assignment_id = ac3.assignment_id
    AND pa2.effective_date
    BETWEEN as3.effective_start_date
    AND as3.effective_end_date
    AND as3.person_id = as2.person_id
    ORDER BY as1.person_id
    , as1.primary_flag DESC
    , as1.effective_start_date
    , act.assignment_id
    FOR UPDATE OF as1.assignment_id
    , pos.period_of_service_id
    Here is the execution plan for this query. We tried adding hints in sub-query to force indexes to pick-up but it is still doing Full table scans.
    Suspecting some db parameter which is causing this issue.
    In the
    - Full table scans on tables in the first sub-query
    PAY_PAYROLL_ACTIONS, PAY_ASSIGNMENT_ACTIONS, PAY_ACTION_INTERLOCKS
    - Full table scans on tables in Second sub-query
    PER_ALL_ASSIGNMENTS_F PAY_ASSIGNMENT_ACTIONS
    call count cpu elapsed disk query current rows
    Parse 1 0.00 0.00 0 0 0 0
    Execute 29 398.80 2192.99 238706 4991924 2383 0
    Fetch 1136 378.38 1921.39 0 4820511 0 1108
    total 1166 777.19 4114.38 238706 9812435 2383 1108
    Misses in library cache during parse: 1
    Misses in library cache during execute: 1
    Optimizer mode: ALL_ROWS
    Parsing user id: 41 (APPS) (recursive depth: 1)
    Rows Execution Plan
    0 SELECT STATEMENT MODE: ALL_ROWS
    0 FOR UPDATE
    0 PX COORDINATOR
    0 PX SEND (QC (ORDER)) OF ':TQ10009' [:Q1009]
    0 SORT (ORDER BY) [:Q1009]
    0 PX RECEIVE [:Q1009]
    0 PX SEND (RANGE) OF ':TQ10008' [:Q1008]
    0 HASH JOIN (ANTI BUFFERED) [:Q1008]
    0 PX RECEIVE [:Q1008]
    0 PX SEND (HASH) OF ':TQ10006' [:Q1006]
    0 BUFFER (SORT) [:Q1006]
    0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF 'PER_ALL_ASSIGNMENTS_F' (TABLE) [:Q1006]
    0 NESTED LOOPS [:Q1006]
    0 NESTED LOOPS [:Q1006]
    0 NESTED LOOPS [:Q1006]
    0 HASH JOIN (ANTI) [:Q1006]
    0 BUFFER (SORT) [:Q1006]
    0 PX RECEIVE [:Q1006]
    0 PX SEND (HASH) OF ':TQ10002'
    0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF 'PAY_ASSIGNMENT_ACTIONS' (TABLE)
    0 NESTED LOOPS
    0 NESTED LOOPS
    0 NESTED LOOPS
    0 NESTED LOOPS
    0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF 'PAY_PAYROLL_ACTIONS' (TABLE)
    0 INDEX MODE: ANALYZED (UNIQUE SCAN) OF 'PAY_PAYROLL_ACTIONS_PK' (INDEX (UNIQUE)
    0 INDEX MODE: ANALYZED (RANGE SCAN) OF 'PAY_POPULATION_RANGES_N4' (INDEX)
    0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF 'PER_PERIODS_OF_SERVICE' (TABLE)
    0 INDEX MODE: ANALYZED (RANGE SCAN) OF 'PER_PERIODS_OF_SERVICE_N3' (INDEX)
    0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF 'PER_ALL_ASSIGNMENTS_F' (TABLE)
    0 INDEX MODE: ANALYZED (RANGE SCAN) OF 'PER_ASSIGNMENTS_N4' (INDEX)
    0 INDEX MODE: ANALYZED (RANGE SCAN) OF 'PAY_ASSIGNMENT_ACTIONS_N51' (INDEX)
    0 PX RECEIVE [:Q1006]
    0 PX SEND (HASH) OF ':TQ10005' [:Q1005]
    0 VIEW OF 'VW_SQ_1' (VIEW) [:Q1005]
    0 HASH JOIN [:Q1005]
    0 BUFFER (SORT) [:Q1005]
    0 PX RECEIVE [:Q1005]
    0 PX SEND (BROADCAST) OF ':TQ10000'
    0 TABLE ACCESS MODE: ANALYZED (FULL) OF 'PAY_PAYROLL_ACTIONS' (TABLE)
    0 HASH JOIN [:Q1005]
    0 PX RECEIVE [:Q1005]
    0 PX SEND (HASH) OF ':TQ10004' [:Q1004]
    0 PX BLOCK (ITERATOR) [:Q1004]
    0 TABLE ACCESS MODE: ANALYZED (FULL) OF 'PAY_ASSIGNMENT_ACTIONS' (TABLE) [:Q1004]
    0 BUFFER (SORT) [:Q1005]
    0 PX RECEIVE [:Q1005]
    0 PX SEND (HASH) OF ':TQ10001'
    0 TABLE ACCESS MODE: ANALYZED (FULL) OF 'PAY_ACTION_INTERLOCKS' (TABLE)
    0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF 'PAY_PAYROLL_ACTIONS' (TABLE) [:Q1006]
    0 INDEX MODE: ANALYZED (UNIQUE SCAN) OF 'PAY_PAYROLL_ACTIONS_PK' (INDEX (UNIQUE)) [:Q1006]
    0 INDEX MODE: ANALYZED (UNIQUE SCAN) OF 'PAY_ACTION_CLASSIFICATIONS_PK' (INDEX (UNIQUE))[:Q1006]
    0 INDEX MODE: ANALYZED (RANGE SCAN) OF 'PER_ASSIGNMENTS_F_PK' (INDEX (UNIQUE)) [:Q1006]
    0 PX RECEIVE [:Q1008]
    0 PX SEND (HASH) OF ':TQ10007' [:Q1007]
    0 VIEW OF 'VW_SQ_2' (VIEW) [:Q1007]
    0 FILTER [:Q1007]
    0 HASH JOIN [:Q1007]
    0 BUFFER (SORT) [:Q1007]
    0 PX RECEIVE [:Q1007]
    0 PX SEND (BROADCAST) OF ':TQ10003'
    0 TABLE ACCESS MODE: ANALYZED (FULL) OF 'PER_ALL_ASSIGNMENTS_F' (TABLE)
    0 PX BLOCK (ITERATOR) [:Q1007]
    0 TABLE ACCESS MODE: ANALYZED (FULL) OF 'PAY_ASSIGNMENT_ACTIONS' (TABLE) [:Q1007]
    Elapsed times include waiting on following events:
    Event waited on Times Max. Wait Total Waited
    ---------------------------------------- Waited ---------- ------------
    enq: KO - fast object checkpoint 32 0.02 0.12
    os thread startup 8 0.02 0.19
    PX Deq: Join ACK 198 0.00 0.04
    PX Deq Credit: send blkd 167116 1.95 1103.72
    PX Deq Credit: need buffer 327389 1.95 266.30
    PX Deq: Parse Reply 148 0.01 0.03
    PX Deq: Execute Reply 11531 1.95 1901.50
    PX qref latch 23060 0.00 0.60
    db file sequential read 108199 0.17 22.11
    db file scattered read 9272 0.19 51.74
    PX Deq: Table Q qref 78 0.00 0.03
    PX Deq: Signal ACK 1165 0.10 10.84
    enq: PS - contention 73 0.00 0.00
    reliable message 27 0.00 0.00
    latch free 218 0.00 0.01
    latch: session allocation 11 0.00 0.00
    Thanks in advance
    Suresh PV

    Hi,
    welcome,
    how is the query performing if you delete all the hints for PARALLEL, because most of the waits are related to waits on Parallel.
    Herald ten Dam
    http://htendam.wordpress.com
    PS. Use "{code}" for showing your code and explain plans, it looks nicer

  • Finding the Text of SQL Query causing Full Table Scans

    Hi,
    does anyone have a sql script, that shows the complete sql text of queries that have caused a full table scan?
    Please also let me know as to how soon this script needs to be run, in the sense does it work only while the query is running or would it work once it completes (if so is there a valid duration, such as until next restart, etc.)
    Your help is appreciated.
    Thx,
    Mayuran

    Finding the Text of SQL Query Causing Full Table Scan

  • Finding the Text of SQL Query Causing Full Table Scan

    Hi,
    does anyone have a sql script, that shows the complete sql text of queries that have caused a full table scan?
    Please also let me know as to how soon this script needs to be run, in the sense does it work only while the query is running or would it work once it completes (if so is there a valid duration, such as until next restart, etc.)
    Your help is appreciated.
    Thx,
    Mayuran

    You might try something like this:
    select sql_text,
           object_name
    from   v$sql s,
           v$sql_plan p
    where  s.address = p.address and
           s.hash_value = p.hash_value and
           s.child_number = p.child_number and
           p.operation = 'TABLE ACCESS' and
           p.options = 'FULL' and
           p.object_owner in ('SCOTT')
    ;Please note that this query is just a snapshot of the SQL statements currently in the cache.

  • Where columnname like '%somevalue' causing full table scan

    hi,
    10.2.0.4 database
    is it possible to force an index scan over a full table scan if I use a where clause similar to the following:
    where col1 like '%somevalue';
    There is an index with col1 as the first segment of the index and another column as the second segment of the index.
    Thanks
    JOhn

    I have done it for you
    SQL> create index empX on emp(job) ;
    Index created.
    SQL> explain plan for select * from emp where job like '%ERK' ;
    Explained.
    SQL> select * from table(dbms_xplan.display) ;
    PLAN_TABLE_OUTPUT
    Plan hash value: 3956160932
    | Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
    |   0 | SELECT STATEMENT  |      |     1 |    37 |     3   (0)| 00:00:01 |
    |*  1 |  TABLE ACCESS FULL| EMP  |     1 |    37 |     3   (0)| 00:00:01 |
    Predicate Information (identified by operation id):
       1 - filter("JOB" LIKE '%ERK')
    13 rows selected.
    SQL> explain plan for select * from emp where job like 'C%ERK' ;
    Explained.
    SQL> select * from table(dbms_xplan.display) ;
    PLAN_TABLE_OUTPUT
    Plan hash value: 140376749
    | Id  | Operation                   | Name | Rows  | Bytes | Cost (%CPU)| Time     |
    |   0 | SELECT STATEMENT            |      |     4 |   148 |     2   (0)| 00:00:01 |
    |   1 |  TABLE ACCESS BY INDEX ROWID| EMP  |     4 |   148 |     2   (0)| 00:00:01 |
    |*  2 |   INDEX RANGE SCAN          | EMPX |     4 |       |     1   (0)| 00:00:01 |
    Predicate Information (identified by operation id):
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    15 rows selected.
    SQL> explain plan for select /*+index (emp,EMPX) */ * from emp where job like '%ERK' ;
    Explained.
    SQL> select * from table(dbms_xplan.display) ;
    PLAN_TABLE_OUTPUT
    Plan hash value: 3745534319
    | Id  | Operation                   | Name | Rows  | Bytes | Cost (%CPU)| Time     |
    |   0 | SELECT STATEMENT            |      |     1 |    37 |     2   (0)| 00:00:01 |
    |   1 |  TABLE ACCESS BY INDEX ROWID| EMP  |     1 |    37 |     2   (0)| 00:00:01 |
    |*  2 |   INDEX FULL SCAN           | EMPX |     1 |       |     1   (0)| 00:00:01 |
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  • Trunc causing Full Table Scans

    I have a situtaion here where my query is as follows.
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    6
    PLAN_TABLE_OUTPUT
    Plan hash value: 3951750498
    | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
    | 0 | SELECT STATEMENT | | 1 | 10 | 13904 (1)| 00:02:47 | | |
    | 1 | SORT AGGREGATE | | 1 | 10 | | | | |
    | 2 | PARTITION LIST SINGLE| | 1 | 10 | 13904 (1)| 00:02:47 | 12 | 12 |
    |* 3 | TABLE ACCESS FULL | HBSM_SM_ACCOUNT_INFO | 1 | 10 | 13904 (1)| 00:02:47 | 12 | 12 |
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    3 - filter(("CUST_STATUS"='UP' OR "CUST_STATUS"='UUP') AND
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    If I remove the trunc clause from the query the performance definitely improves the the results are wrong.
    SQL> select count(1) from HBSM_SM_ACCOUNT_INFO where OPTIONAL_PARM5='MH' and CUST_STATUS in ('UP','UUP') and FIRST_ACTVN_DATE = trunc(sysdate);
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    0
    PLAN_TABLE_OUTPUT
    Plan hash value: 454529511
    | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
    | 0 | SELECT STATEMENT | | 1 | 40 | 47 (0)| 00:00:01 | | |
    |* 1 | TABLE ACCESS BY GLOBAL INDEX ROWID| HBSM_SM_ACCOUNT_INFO | 1 | 40 | 47 (0)| 00:00:01 | 12 | 12 |
    |* 2 | INDEX RANGE SCAN | IND_FIRST_ACTVN_DATE | 51 | | 4 (0)| 00:00:01 | | |
    Can someone please help me whereby I can get the right data and I can also prevent these full table scans.

    Unless you are using a functional index, applying any function to an indexed column prevents the use of the index.
    The way round it in your case is to realise that
    select count(1) from HBSM_SM_ACCOUNT_INFO where OPTIONAL_PARM5='MH' and CUST_STATUS in ('UP','UUP') and trunc(FIRST_ACTVN_DATE) = trunc(sysdate)Is really asking that FIRST_ACTVN_DATE should be sometime today. You could therefore rewrite it as
    select count(1) from HBSM_SM_ACCOUNT_INFO where OPTIONAL_PARM5='MH' and CUST_STATUS in ('UP','UUP')
    and FIRST_ACTVN_DATE >= trunc(sysdate)
    and FIRST_ACTVN_DATE < trunc(sysdate) + 1Note, this still might not use the index depending on how many rows are within today's date versus how many are outside today's date.
    Also, when posting, remember to put your code between tags and to post create table scripts and sample data inserts.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   

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