Need some assistance with an SQL query

I have two files, one is a work file with 991 records and the other is a
production (Test Environment) file with 22 mil. I am updating the
production records that match to records in the work file.

Here is my sql statement:
Exec Sql
Update RoutMaxl1 as a
Set a.mxUdt = :xDate,
a.mxUtm = :xTime,
a.mxUop = 'CPP989825645KY',
a.mxCpdy = 'Y',
a.mxUty = 'C'
Where exists
(select * from xRouteMax as b
where a.mxplan = b.mxplan and
a.mxdiv = b.mxdiv and
a.mxins = b.mxins and
a.mxben = b.mxben and
a.mxppo = b.mxppo and
a.mxtfrm = 'V' and
a.mxtdt = 0);

The statement runs fine but I only update 980 records, which means that I
have 11 records in table A (xRouteMax) that do not exist in table B.

Suggestion on how to get a list of those records? I just want the 11.