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Don Burleson Blog 







impdp import with ORA-04020 error

Oracle Database Tips by Donald BurlesonNovember 9, 2015

Question:  I am running a data pump impdp import and I get the ORA-04020 error:

impdp user/pwd directory=data_pump_dir dumpfile=exp_test.dmp logfile=imp_test.log table_exists_action=replace

*** 2015-11-09 10:23:27.799
A deadlock among DDL and parse locks is detected.
This deadlock is usually due to user errors in
the design of an application or from issuing a set
of concurrent statements which can cause a deadlock.
This should not be reported to Oracle Support.
The following information may aid in finding
the errors which cause the deadlock:
ORA-04020: deadlock detected while trying to lock object MV_LOTS

How do I resolve this ORA-04030 error?

Answer:  I assume by the object name (MV_LOTS) that this is happening with a materialized view. 

This error message relates to library cache lock deadlocks, not enqueue lock deadlocks. To investigate library cache locking issues, you need to use DBA_KGLLOCK which is created by the $ORACLE_HOME/rdbms/admin/catblock.sql script." 

Here are my general notes on the ORA-04020 error: ORA-04020_deadlock_detected_while_trying_to_lock_object.

I Googled this impdp ORA-04020 error and some say that a solution for a ORA-04020 in impdp includes:

1 - Bounce the database and try the import again

2 - See MOSC, this may be bug 4454890

3 - Read note Note: 360509.1 on MOSC

4 - Bypass the materialized view and try refreshing it again, when it is guaranteed not to be in the process of refreshing.

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