Do Not Use Parallel Query In ALTER TABLE MODIFY (column Not Null)

(Doc ID 2264469.1)

Last updated on JUNE 30, 2017

Applies to:

Oracle Database - Enterprise Edition - Version 12.2.0.1 and later
Information in this document applies to any platform.

Symptoms

You are modifying table with mutli billion rows.  Specific column was nullable and became not null

The time to change constraint takes  around 40 minutes.

Mainly due to execution

SELECT /* all_rows ordered dynamic_sampling(2) */ A.rowid,:1,:2,:3 from "TCTDBS"."ARCHORIGINALPOS" A WHERE ( "COMAMOUNT" is NULL)

this query is running without parallelism

You specifically run
ALTER SESSION FORCE PARALLEL DML PARALLEL 8
/
ALTER SESSION FORCE PARALLEL QUERY PARALLEL 8
/
ALTER SESSION FORCE PARALLEL DDL PARALLEL 8
/

But it still does not use parallelism

Any option to force parallelism?

Cause

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