How to update a table having millions of records faster?

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SQL-Server

I have to update a table which has million of records.

I have used the below query.

1.I have put the pkeys to be updated in a temp table

select * into tempPkey  
  from Prd WHERE status<>'d' and pKey NOT IN (SELECT PrdPKey FROM PrdGroupRel where status <>'d')

2. Then i have use below update command to update.

SET NOCOUNT ON
DECLARE    @PKey  AS Varchar(16) ;

DECLARE UPDATE_CURSOR CURSOR FOR

SELECT pkey FROM tempPkey FOR UPDATE 

OPEN UPDATE_CURSOR
FETCH NEXT FROM UPDATE_CURSOR
INTO @PKey

WHILE (@@FETCH_STATUS = 0)
BEGIN
BEGIN Transaction



Update Cndcpmain set status ='d' ,Hostsource='INC7892752_30Oct2018'  
where mergedkey like '%'+@PKey+'%'  and CndcpMetapkey='00100000007gu6ib' and salesorg='MS01' and status<>'d'

Print 'Pkey Update completed :' + @Pkey+' ' + convert(varchar(50),Getdate() )

COMMIT Transaction  
    FETCH NEXT FROM UPDATE_CURSOR
    INTO @PKey
END

CLOSE UPDATE_CURSOR
DEALLOCATE UPDATE_CURSOR

SET NOCOUNT OFF

I have disabled triggers and indexes on Cndcpmain table. but only 14-15 pkeys are getting updated in 1 min. There are total 18916 pkeys to update and expected time is 20 hrs. Can we expedite it?

Also I unable to write a select query for the records which got already updated ,so that i can exclude the updated records in next run. could you please help

What I have tried:

[See code above]