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DB File Parallel Read, Sequential Read and Scattered Read in Same Operation

Orcl ApexMar 24 2018 — edited Mar 26 2018

Hi All,

I am seeing a strange where oracle is doing DB File Parallel Read, Sequential Read and Scattered Read in same operation. May be it's strange case for me only.

Can you help me understanding why oracle is doing so on id 23.

===========================================================================================================================================================================================================

| Id |                   Operation                   |          Name          |  Rows   | Cost  |   Time    | Start  | Execs |   Rows   | Read  | Read  |  Mem  | Activity |       Activity Detail        |

|    |                                               |                        | (Estim) |       | Active(s) | Active |       | (Actual) | Reqs  | Bytes | (Max) |   (%)    |         (# samples)          |

===========================================================================================================================================================================================================

|  0 | SELECT STATEMENT                              |                        |         |       |         9 |    +75 |     1 |    16082 |       |       |       |          |                              |

|  1 |   SORT ORDER BY                               |                        |       1 | 44593 |         9 |    +75 |     1 |    16082 |       |       |    2M |          |                              |

|  2 |    HASH JOIN OUTER                            |                        |       1 | 44592 |        72 |     +4 |     1 |    16082 |       |       |    3M |          |                              |

|  3 |     VIEW                                      |                        |       1 | 34319 |         1 |     +4 |     1 |    16082 |       |       |       |          |                              |

|  4 |      HASH GROUP BY                            |                        |       1 | 34319 |         1 |     +4 |     1 |    16082 |       |       |    4M |          |                              |

|  5 |       HASH JOIN OUTER                         |                        |       7 | 34318 |         2 |     +3 |     1 |       1M |       |       |  115M |     1.35 | Cpu (1)                      |

|  6 |        HASH JOIN                              |                        |       7 | 34220 |         1 |     +4 |     1 |       1M |       |       |    2M |          |                              |

|  7 |         TABLE ACCESS FULL                     | XXPO01_LAYOUT          |   15971 |    83 |         1 |     +4 |     1 |    16126 |       |       |       |          |                              |

|  8 |         TABLE ACCESS BY INDEX ROWID BATCHED   | XXPO01_INBOUND         |    120K | 34135 |         4 |     +1 |     1 |       1M |       |       |       |     2.70 | Cpu (2)                      |

|  9 |          INDEX RANGE SCAN                     | XXPO01_INBOUND_N02     |    724K |  1769 |         1 |     +4 |     1 |       1M |       |       |       |          |                              |

| 10 |        VIEW                                   |                        |    7216 |    98 |         1 |     +4 |     1 |    15465 |       |       |       |          |                              |

| 11 |         WINDOW BUFFER                         |                        |    7216 |    98 |         1 |     +4 |     1 |    15465 |       |       |  499K |          |                              |

| 12 |          SORT GROUP BY                        |                        |    7216 |    98 |         1 |     +4 |     1 |    15465 |       |       |  757K |          |                              |

| 13 |           TABLE ACCESS FULL                   | XXPO01W_AUDIT          |    7238 |    97 |         1 |     +4 |     1 |    24503 |       |       |       |          |                              |

| 14 |     VIEW                                      |                        |       1 | 10273 |         1 |    +75 |     1 |    16091 |       |       |       |          |                              |

| 15 |      HASH GROUP BY                            |                        |       1 | 10273 |        72 |     +4 |     1 |    16091 |       |       |    4M |          |                              |

| 16 |       NESTED LOOPS                            |                        |       1 | 10272 |        72 |     +4 |     1 |       1M |       |       |       |     1.35 | Cpu (1)                      |

| 17 |        NESTED LOOPS                           |                        |     782 | 10272 |        72 |     +4 |     1 |       1M |       |       |       |          |                              |

| 18 |         NESTED LOOPS                          |                        |     782 |  8393 |        72 |     +4 |     1 |       1M |       |       |       |          |                              |

| 19 |          NESTED LOOPS                         |                        |     994 |  5207 |        72 |     +4 |     1 |    20678 |       |       |       |          |                              |

| 20 |           TABLE ACCESS FULL                   | RCV_SHIPMENT_HEADERS   |     994 |  2818 |        72 |     +4 |     1 |    20682 |    50 | 544KB |       |     1.35 | Cpu (1)                      |

| 21 |           TABLE ACCESS BY INDEX ROWID BATCHED | AP_INVOICES_ALL        |       1 |     2 |        72 |     +4 | 20682 |    20678 |       |       |       |          |                              |

| 22 |            INDEX RANGE SCAN                   | AP_INVOICES_N6         |       1 |     2 |        72 |     +4 | 20682 |    20678 |   106 | 848KB |       |          |                              |

| 23 |          TABLE ACCESS BY INDEX ROWID BATCHED  | AP_INVOICE_LINES_ALL   |       1 |     3 |        72 |     +4 | 20678 |       1M | 82174 | 645MB |       |    54.05 | db file parallel read (5)    |

|    |                                               |                        |         |       |           |        |       |          |       |       |       |          | db file scattered read (1)   |

|    |                                               |                        |         |       |           |        |       |          |       |       |       |          | db file sequential read (34) |

| 24 |           INDEX RANGE SCAN                    | AP_INVOICE_LINES_U1    |      12 |     2 |        72 |     +4 | 20678 |       1M |       |       |       |          |                              |

| 25 |         INDEX RANGE SCAN                      | RCV_SHIPMENT_LINES_N4  |       1 |     2 |        72 |     +4 |    1M |       1M |  1365 |  11MB |       |     4.05 | Cpu (3)                      |

| 26 |        TABLE ACCESS BY INDEX ROWID            | RCV_SHIPMENT_LINES     |       1 |     2 |        72 |     +4 |    1M |       1M | 42660 | 335MB |       |    35.14 | Cpu (3)                      |

|    |                                               |                        |         |       |           |        |       |          |       |       |       |          | db file scattered read (2)   |

|    |                                               |                        |         |       |           |        |       |          |       |       |       |          | db file sequential read (21) |

===========================================================================================================================================================================================================

This post has been answered by Jonathan Lewis on Mar 26 2018
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