DB2 11.5 Change GENERATED BY DEFAULT FOR EACH ROW ON UPDATE AS ROW CHANGE TIMESTAMP column

DB2 11.5 on Windows.

We added this column to most of our tables to see when last update was made for a replication project in SSIS.  

DW_LASTTIME   TIMESTAMP   NOT NULL   GENERATED BY DEFAULT FOR EACH ROW ON UPDATE AS ROW CHANGE TIMESTAMP

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The project died on the vine and I just found out that my online reorg script has been failing with this error.

Online Reorg fails with SQL2219N Reason code: "13"
https://www.ibm.com/support/pages/online-reorg-fails-sql2219n-reason-code-13

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I can't start doing offline reorgs due to the nature of the business so I would like to change that column to just a regular timestamp or date or varchar.

ALTER table TESTTABLE  ALTER COLUMN DW_LASTTIME SET DATA TYPE VARCHAR(30);

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But when I try I get

ERROR [42837] [IBM][DB2/NT64] SQL0190N  ALTER TABLE "AE" specified attributes for column "DW_LASTTIME" that are not compatible with the existing column.

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I know I can drop it but I was trying to be less intrusive.  Is there any way to change this sort of dropping the column?
Thanks!
Jim