I am new to teradata. I have several stage tables defined as NoPI.
I notice most stage talbes have skew factor > 50. Is there a way to reduce this.
What is the best way to handle this situation for stage tables with NoPI?
Any ideas. please advise.
How large are those tables?
And how are they loaded?
These are probably small tables tables loaded with batch load TD utility.
Even though it is true that your NoPI tables will be loaded in round robin manner in this case, the round robin is applied on block level (not row level).
This implies that in the case of small tables that fit in one (a couple) of blocks, all the data will end up on a single (a couple) of AMPs. That should explain the high skew factor.
I would recommend distributing those tables on appropriate PI column.
You won't get any benefits on FastLoading a small NoPI table.
I have same problem.
My Table size 480 GigaByte and skew factor > 78 . It is 7 column table(Using 3 Column as primary Index).
I create also NoPI table but still skew factor is same.
How i reduce it ? Please help me.
If you created the NoPI table from the PI Table the skew will be the same (AMP local). You must create the NoPI table EMPTY and load it from scratch. This should guarantee a good distribution (e.g.: low skew).
In TD14 there's also a new option for INSERT/SELECT into NoPI tables, HASH BY RANDOM, to reduce skew.