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Parallel Query Runs in Serial ON RAC when Using Default SERVICE_NAME (Doc ID 2603641.1)

Last updated on JUNE 02, 2023

Applies to:

Oracle Database - Enterprise Edition - Version and later
Gen 2 Exadata Cloud at Customer - Version All Versions and later
Information in this document applies to any platform.


NOTE: In the images and/or the document content below, the user information and environment data used represents fictitious data from the Oracle sample or bulit-in schema(s), Public Documentation delivered with an Oracle database product or other training material.  Any similarity to actual environments, actual persons, living or dead, is purely coincidental and not intended in any manner.
  1. A query runs serially when connecting to the database using the default PDB SERVICE_NAME. It runs in parallel if connecting to the database using SID, or using a non-default SERVICE_NAME.
           Example: select /*+ parallel(8) full(t) */ count(1)  from  <table> t;
  2. The service can often be seen as active in the listener (lsnrctl status), but could also be absent.

  3. The PDB name is not listed in gv$active_services, although it may be listed in gv$services.

  4. A PX trace shows that there are 0 instances available to run in parallel.

Example PX trace file:





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