whether row hash changes when new nodes or Amp added?

Database

whether row hash changes when new nodes or Amp added?

Hi All,
As I am going to prepare for PI and puzzled in few questions, looking to find the answer of these questions...

whether hash row changes when we add new AMPs or Nodes in the existing Teradata System....?

can any body put more lights on it....

Thanks in Advance....

5 REPLIES
N/A

Re: whether row hash changes when new nodes or Amp added?

Hi

Yes it will, providing you have more AMP's. The Row hash is always the same and a record will always be put on the same AMP but if you upgrade you system and add more AMP's this will change and not all rows will be on the same AMPs.

Re: whether row hash changes when new nodes or Amp added?

As you said row hash will change. Before upgrading are they going to empty the records? then reloaded to allow wider distribution of records? I am not clear about already exsting records how they will be treated.
Please clarify me.

with regards,

shankarkanth
Teradata Employee

Re: whether row hash changes when new nodes or Amp added?

RowHash does NOT change. Only HashMap (which RowHash values go to which AMP) changes.
N/A

Re: whether row hash changes when new nodes or Amp added?

You could HASH functions to check this before and after upgrade.

Vinay
Teradata Employee

Re: whether row hash changes when new nodes or Amp added?

Correct. You should find:
HASHROW(...) does not change
HASHBUCKET(HASHROW(...)) does not change
HASHAMP(HASHBUCKET(HASHROW(...))) does change for some values