Avoid parent child dimensions?!? 
Author Message
 Avoid parent child dimensions?!?

Hi all,
I have learned that using parent child dimensions,
although they supported by Analysis Services, is not
useful, since they do not preaggregate. I understand that
for writeback in dimensions a parent child dimension is
needed (For a new level in the dim a row would have to be
added to the sourcetable?!).

Are there any other reasons for using p-c-dimensions?

Our specific problem is, that the CRM system our client
uses (Siebel, contains the OLTP data) is designed to be
as dynamic as possible. Meaning almost every table
contains a p-c-dimension. So far we have just moved
selected data "as is" into a separate p-c-table and used
it as a Parent child dimension.

Is there a generalized way to change from pc to star or
snowflake design?

Thanks in advance...

Lutz



Tue, 27 Sep 2005 14:49:21 GMT
 Avoid parent child dimensions?!?

You can use it if you have data on different levels in the fact table. One
example is overhead costs that you would like to allocate to products. This
is also the only dimension that supports parent-child hierarchies like
organizational structures and account structures.

Parent-Child dimensions are good if you do not misuse them but understand
their pros and cons.

HTH
Thomas Ivarsson
DW-Consultant Malm? Sweden


Quote:
> Hi all,
> I have learned that using parent child dimensions,
> although they supported by Analysis Services, is not
> useful, since they do not preaggregate. I understand that
> for writeback in dimensions a parent child dimension is
> needed (For a new level in the dim a row would have to be
> added to the sourcetable?!).

> Are there any other reasons for using p-c-dimensions?

> Our specific problem is, that the CRM system our client
> uses (Siebel, contains the OLTP data) is designed to be
> as dynamic as possible. Meaning almost every table
> contains a p-c-dimension. So far we have just moved
> selected data "as is" into a separate p-c-table and used
> it as a Parent child dimension.

> Is there a generalized way to change from pc to star or
> snowflake design?

> Thanks in advance...

> Lutz



Tue, 27 Sep 2005 23:06:43 GMT
 Avoid parent child dimensions?!?
Thomas, thanks for responding.
My problem is, I am unsure that we are doing the right
thing by using parent child dimensions almost exclusively.

We use it in cases where it is used in the source system
and stick to it for reasons of simplicity. if the levels
of a hierarchy are known, should one transform from
parent child structure to snowflakeing?

Please give a clue, anyone.

THX Lutz



Sat, 01 Oct 2005 22:59:41 GMT
 Avoid parent child dimensions?!?
Hi Lutz

If your hierarcy is balanced (or close to it) it is generally better, for
performance reason, to prefer regular dimension to parent/child.

Another advantage is the the regular dimension can be more intuitive for the
users, specifically because the levels of the dimension can be named in a
consistent manner

--
Sincerely
Thomas Kejser

M. Sc., MCDBA, MCP + Site Building


Quote:
> Thomas, thanks for responding.
> My problem is, I am unsure that we are doing the right
> thing by using parent child dimensions almost exclusively.

> We use it in cases where it is used in the source system
> and stick to it for reasons of simplicity. if the levels
> of a hierarchy are known, should one transform from
> parent child structure to snowflakeing?

> Please give a clue, anyone.

> THX Lutz



Sun, 02 Oct 2005 01:49:27 GMT
 Avoid parent child dimensions?!?
If you have a dimension where all data can be entered in the leaf/lowest
level you should use a regular dimension for performance reasons.
Snowflakeing or not, you can use both in a standard dimension.

HTH
Thomas Ivarsson


Quote:
> Thomas, thanks for responding.
> My problem is, I am unsure that we are doing the right
> thing by using parent child dimensions almost exclusively.

> We use it in cases where it is used in the source system
> and stick to it for reasons of simplicity. if the levels
> of a hierarchy are known, should one transform from
> parent child structure to snowflakeing?

> Please give a clue, anyone.

> THX Lutz



Sun, 02 Oct 2005 02:05:51 GMT
 
 [ 5 post ] 

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