If the job owner has 'sa' level permissions, then the job is run under the Agent's service account, and thus using its permissions to other resources -- drives, network, etc..

I assume you have space in prod to restore the db to a diff name?

If so, you could:

1) restore the db to a diff name
2)...

To avoid having to lookup every duplicate tab1.col1 value in tab2, which is pointless, I'd try this query:

SELECT t1.col1
FROM (
  SELECT DISTINCT col1...

SQL has a very strong built-in preference...

Some quick thoughts:

1. Why not a 5-minute interval?  I don't know of anything other than a payment system that would need a lower interval than that.

2....

Since you've very likely to (almost) always query by trans date, you should change the clustering on the table to:
( [transactionDate], [transactionId] )

That will help performance for...

Certain errors cause SQL to exit the batch, no matter what the code says.

You shouldn't really need to completely flush the buffers.  Comparing Logical I/O should be sufficient, since you can't really know what physical I/O will occur for any given query at...

But that doesn't match your original request.  You said you wanted "records" (i.e. rows), which would include the Due_time.

If you need just the client_id and PU, you can...

SELECT tn.*
FROM dbo.table_name tn
INNER JOIN (
    SELECT client_id,PU
    FROM dbo.table_name
    GROUP BY client_id,PU
    HAVING MIN(Due_time) <> MAX(Due_time)

If you're on SQL 2016, you should use SQL's native data masking capability.  It will easily and efficiently do exactly what you want.

If that won't work, you could...

(1) Get rid of the ActiveStatus column.  It's useless, and it can cause headaches for the optimizer.  That type of column really is a throwback to tape-based data.

(2) At...