Update millions of rows in very huge table Performance

/*Use set value also in where clause.

Eg. Set nUsablePledgestock=1

Where nUsablePledgestock !=0

"/

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where nUsablepledgestock!=Quantity ;

Commit ;

/* split the query to month-wise */

Following will not increase undo in very high amount.

set timing on

spool d:\poaupdate.txt

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran <='01-APR-2019' and nUsablepledgestock!=Quantity; 

Commit ;

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran >'01-APR-2019' and dtoftran <='01-MAY-2019' and nUsablepledgestock!=Quantity; 

Commit ;

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran >'01-MAY-2019' and dtoftran <='01-JUN-2019' and nUsablepledgestock!=Quantity; 

Commit ;

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran >'01-JUN-2019' and dtoftran <='01-JUL-2019' and nUsablepledgestock!=Quantity; 

Commit ;

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran >'01-JUL-2019' and dtoftran <='01-AUG-2019' and nUsablepledgestock!=Quantity; 

Commit ;

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran >'01-AUG-2019' and dtoftran <='01-SEP-2019' and nUsablepledgestock!=Quantity; 

Commit ;

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran >'01-SEP-2019' and dtoftran <='01-OCT-2019' and nUsablepledgestock!=Quantity; 

Commit ;

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran >'01-OCT-2019' and dtoftran <='01-NOV-2019' and nUsablepledgestock!=Quantity; 

Commit ;

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran >'01-NOV-2019' and dtoftran <='01-DEC-2019' and nUsablepledgestock!=Quantity; 

Commit ;

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran >'01-DEC-2019' and dtoftran <='01-JAN-2020' and nUsablepledgestock!=Quantity; 

Commit ;

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran >'01-JAN-2020' and dtoftran <='01-FEB-2020' and nUsablepledgestock!=Quantity; 

Commit ;

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran >'01-FEB-2020' and dtoftran <='01-MAR-2020' and nUsablepledgestock!=Quantity; 

Commit ;

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran >'01-MAR-2020' and dtoftran <='01-APR-2020' and nUsablepledgestock!=Quantity; 

Commit ;

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran >'01-APR-2020' and dtoftran <='01-MAY-2020' and nUsablepledgestock!=Quantity; 

Commit ;

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran >'01-MAY-2020' and dtoftran <='01-JUN-2020' and nUsablepledgestock!=Quantity; 

Commit ;

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran >'01-JUN-2020' and dtoftran <='01-JUL-2020' and nUsablepledgestock!=Quantity; 

Commit ;

Update PowerofAttorneystocks set nUsablePledgestock=Quantity Where firmnumber='CUB-000001' and dtoftran >'01-JUL-2020' and nUsablepledgestock!=Quantity; 

Commit ;

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spool off