-- I use a table to log the start and finish time, package name, number of rows inserted and number of rows updated
insert into SSIS_Log
 (PackageName,DTStart)
 values
 (?,GetDate()); -- Map the System variable "PackageName"

declare 
        @mergeResultsTable table (MergeAction VARCHAR(20)); 
 
declare 
        @insertCount int, 
        @updateCount int;


MERGE Table_A AS TARGET
USING (
SELECT	
	 Col1
	,Col2
	.....
	,ColN
FROM	Table_B
) AS SOURCE 
ON (TARGET.Key1 = SOURCE.Key1 and TARGET.Key_2 = SOURCE.Key_2)
-- Update
WHEN MATCHED THEN UPDATE SET
       TARGET.Col1= SOURCE.Col1
      ,TARGET.Col2= SOURCE.Col2
	  ,TARGET.UpdateDT=GetDate() -- I create a UpdateDT column in the target table to store the update datetime
	  -- etc
--Insert
WHEN NOT MATCHED BY TARGET THEN INSERT
(
       Col1
      ,Col2
	  ,CreateDT -- I create a CreateDT column in the target table to store the insert (or creation) datetime
	  -- etc
)
VALUES
(	   SOURCE.Col1
	  ,SOURCE.Col2
	  ,GetDate()
	  -- etc
)

OUTPUT $action into @mergeResultsTable;  

update SSIS_Log
set UpdatedCount =        -- Log the count of updated rows
(SELECT COUNT(*)  
FROM @mergeResultsTable 
WHERE MergeAction = 'UPDATE')
, InsertedCount =         -- Log the count of inserted rows
(SELECT COUNT(*)  
FROM @mergeResultsTable 
WHERE MergeAction = 'INSERT')
,DTFinish = GetDate()
where Idx =
 (
  select MAX(Idx)
  from SSIS_Log
 );