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Expdp is Slow with 'DB file Sequential Read' on Table with Chained Rows (Doc ID 2033737.1)

Last updated on FEBRUARY 27, 2019

Applies to:

Oracle Database - Enterprise Edition - Version 11.2.0.1 to 12.1.0.1 [Release 11.2 to 12.1]
Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Information in this document applies to any platform.

Symptoms

Expdp is very slow for some tables with waits on 'db file sequential read'.

Tracing shows that majority of the waits are on statements like below:

SELECT *
FROM
RELATIONAL("<SCHEMA_NAME>"."<TABLE_NAME>");


call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
Parse        1      0.01       0.00          0         43          0           0
Execute      0      0.00       0.00          0          0          0           0
Fetch        0      0.00       0.00          0          0          0           0
------- ------  -------- ---------- ---------- ---------- ----------  ----------
total        1      0.01       0.00          0         43          0           0

Misses in library cache during parse: 1
Optimizer mode: CHOOSE
Parsing user id: SYS   (recursive depth: 2)

Elapsed times include waiting on following events:
 Event waited on                             Times   Max. Wait  Total Waited
 ----------------------------------------   Waited  ----------  ------------
 db file sequential read                    995456        0.02        150.55
 direct path read                               72        0.01          0.04
 db file parallel read                           1        0.02          0.02
********************************************************************************

 

Changes

 

Cause

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In this Document
Symptoms
Changes
Cause
Solution
References


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