True or False – Data Dump Import and Indexes

6 05 2010

May 6, 2010

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While reading one of the OTN threads that asked whether Data Pump import will automatically rebuild indexes, I notice that someone posted an interesting response that appeared to be quoted from another source.  I searched the Internet and found the text that was copied into the OTN post, directly below a heading that read “Maximizing Oracle Import (impdp) Performance” – it was then that I decided it was time for another true or false quiz.

The reading material:

  1. http://www.dba-oracle.com/oracle_tips_load_speed.htm
  2. http://download.oracle.com/docs/cd/E14072_01/server.112/e10701/dp_import.htm
  3. http://download.oracle.com/docs/cd/E14072_01/server.112/e10701/dp_export.htm

Read through the above material and attempt to answer the following questions – as in the past, state why the answer is true or false.  Since the first article was last revised in March 2006, I probably should have referenced the documentation for Oracle Database 10g R2, but the Oracle Database 11g R2 documentation should be sufficient.

1.  The options used when data is exported with Data Pump Export (expdp) have no control over how the data may be imported with Data Pump Import (impdp).

2.  Data Pump Export supports enabling and disabling direct path for exports.

3.  Set the ANALYZE parameter of impdp to N to prevent statistics from being gathered on imported tables and indexes.

4.  Using solid state disks (SSD) will speed up import rates when the import job is otherwise fully tuned.

5.  Setting the COMMIT parameter of impdp to N suppresses the committing of the imported data until the load process ends.

6.  Setting the INDEXES parameter of impdp to N prevents indexes from being created until the import process completes.

7.  Setting the INDEXES parameter of impdp to N eliminates the index maintenance overhead when data is imported into a pre-existing table having pre-existing indexes.

8.  When the creation of indexes is postponed through the use of the INDEXES parameter of impdp, the resulting text file should be edited to set the parallel degree of each index to one less than the value of the CPU_COUNT initialization parameter’s value.

9.  Using the EXCLUDE=STATISTICS parameter value of impdp prevents the automatic of gathering of object statistics by impdp.  Setting this parameter value will greatly improve impdp performance.

10. When the _disable_logging initialization parameter is set to TRUE, either a SHUTDOWN ABORT or instance crash will disable/corrupt the database.  This corruption may be prevented by creating a backup of the database before modifying the value of that hidden initialization parameter.

Edit – May 6, 2010: The original title of this blog article was intended to be “True or False – Data Pump Import and Indexes” – a bit of unintentional humor was caused by the typo in the article title.  There are several definitions of the word “Dump“, some of which are more fitting than others.

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