DataPump Import Via NETWORK_LINK Is Slow With CURSOR_SHARING=FORCE (Doc ID 421441.1)

Last updated on MAY 19, 2017

Applies to:

Oracle Database - Enterprise Edition - Version 9.2.0.6 to 10.2.0.3 [Release 9.2 to 10.2]
Information in this document applies to any platform.
*** Checked for relevance on 170Nov-2016 ***

Symptoms

DataPump import with NETWORK_LINK is being considered to migrate to a new database. But DataPump import is going slow while running a query for the estimation phase which tries to determine whether the table to be imported is empty or not.

Below query performs a full table scan which doubles the cost of DataPump import.

SELECT NVL((SELECT /*+ NESTED_TABLE_GET_REFS */ 1
FROM t@target.db WHERE ROWNUM = 1),0)
FROM dual;

This query also results in too many network packets which makes the performance much worse.

Step to reproduce, e.g.

# impdp tc/tc tables=t network_link=target.db

Changes

CURSOR_SHARING on the source site has been set to FORCE or SIMILAR.

Cause

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