Teradata recommends a data skew threshold of no more than 5% across the AMPs . It is a rule of thumb, but not absolute. Small tables can be skew by their nature.

 

select

    hashamp(hashbucket(hashrow(<PRIMARY_INDEX>))) as "AMP",

    count(*)                                    as "row count",

    "row count" * 100.00 / sum("row count") over() as "% of total rows",

    cast((max("row count") over() - min("row count") over()) * 100.00 /

                             nullif(min("row count") over(),0)

         as decimal(9,2)) as "Teradata variance %",

    case

        when "Teradata variance %" < 5

        then 'pass'

        else 'fail'

      end as "Teradata threshold (5%)"

from  <DATABASE_NAME>.<TABLE_NAME>

group by 1

order by 1;

 

Example:

select

    hashamp(hashbucket(hashrow(Sales_Tran_Seq_Num))) as "AMP",

    count(*)                                    as "row count",

    "row count" * 100.00 / sum("row count") over() as "% of total rows",

    cast((max("row count") over() - min("row count") over()) * 100.00 /

                             nullif(min("row count") over(),0)

         as decimal(9,2)) as "Teradata variance %",

    case

        when "Teradata variance %" < 5

        then 'pass'

        else 'fail'

      end as "Teradata threshold (5%)"

from  DB.SALES_TRANSACTION

group by 1

order by 1;

AMP	row count	% of total rows	Teradata variance %	Teradata threshold (5%)
0	47479010	5.00	0.24	pass
1	47510704	5.01	0.24	pass
2	47395857	4.99	0.24	pass
3	47506480	5.01	0.24	pass
4	47440605	5.00	0.24	pass
5	47400512	5.00	0.24	pass
6	47444403	5.00	0.24	pass
7	47407178	5.00	0.24	pass
8	47476876	5.00	0.24	pass
9	47445181	5.00	0.24	pass
10	47437059	5.00	0.24	pass
11	47399911	5.00	0.24	pass
12	47449336	5.00	0.24	pass
13	47409955	5.00	0.24	pass
14	47461295	5.00	0.24	pass
15	47463932	5.00	0.24	pass
16	47454532	5.00	0.24	pass
17	47413774	5.00	0.24	pass
18	47440080	5.00	0.24	pass
19	47447863	5.00	0.24	pass