How to work around ORA-14402: updating partition key column would cause a partition change

The error

ORA-14402: updating partition key column would cause a partition change

occurs when you try to update the value of a partition key column.
This will lead to an implicit INSERT operation.
The ROWID of the row was assigned when the row was first inserted, and it doesn't change. Therefore, by default, Oracle will reject any DML that will cause a rowid to be changed.

Example:

update sales.quarterly_sales
set sold_month = '2016-02'
WHERE unique_sales_id = '3d6fb1ad-243d-4435-97d8-9ca4bfde3ab5';

Since the partition key is the column "sold_month", it will return ORA-14402.

The workaround is to allow row movement for the table:

alter table sales.quarterly_sales enable row movement;

You can now update the row.

You may want to revoke the permission for the rows in the table to change rowid when you are finished:

alter table sales.quarterly_sales disable row movement;

Further reading:
Doc ID 1518567.1 "FAQ: Row Movement Common Questions and Problems on Partitioned Tables"
Doc ID 236191.1: "Updating Partition Key Column Fails with ORA-14402"