Backend design

Question

Hi,
The scenario we have is that we have backend design done in two ways.
Let me explain both the structures completely.
1.We have 2 layers.In the 1st layer we have 3 ODS with full update and then on top of it 3 Infocubes with delta update from the underlying ODS's.Then the data from the cubes in the lower layer goes to the 3 cubes in the upper layer.And then a multiprovider is built on these upper layer cubes on which reporting is done.
2. Here also we have 2 layers.In the lower layer we have 3 ODS with full update.then another layer with 3 ODS with delta update and then these 3 ODS's feed 3 cubes in the upper layer .rest all remain same.
in short,we have cubes with delta update in the first structure and ODS with delta update in the second structure.
Can some one please explain which of this is better and why?
Please reply.
Regards,
Suchitra

Answer 1

Hi,
As per your scenario we are using cube as the reporting layer using multiprovider in first case and ODS as the reporting layer in the second case.Now the diffrence in both cases can be categorized in 2 ways:
1.Architecture Wise
2.Reporting Wise.
Architecture Wise:
we will have the following diffrences
one major difference is the manner of data storage. In ODS, data is stored in flat tables. By flat we mean to say ordinary transparent table whereas in a CUBE, it composed of multiple tables arranged in a STAR SCHEMA joined by SIDs. The purpose is to do MULTI-DIMENSIONAL Reporting
Another difference is In ODS, you can update an existing record given the KEY. In CUBES, theres no such thing. It will accept duplicate records and during reporting, SUM the keyfigures up. Theres no EDIT previous record contents just ADD. With ODS, the procedure is UPDATE IF EXISTING (base from the Table Key) otherwise ADD RECORD.
Reporting Wise:
basically you use ods-objects to store the data on a document/item/schedule line level whereas in the cube you will have only more aggregated data (on material, customer ...). So you can do your reporting on the already aggregated data and if necessary do a detailed reporting on the ods object. Addionally ods objects will provide you a delta in case your datasource doesn't provide it. Just use overwrite mode for all (characteristics and keyfigures) in the update rules and the ods will take care about the rest
Infocubes are Multi dimensional objects that contains fact table and dimension table are available whereas ODS is not a multi dimensional object there are no fact tables and dimension tables. It consists of flat transparent tables.
In infocubes there are characteristics and keyfigures but in ods key fields and data fields. we can keep non key characteristics in data fields.
Some times we need detailed reports we can get through ODS. ODS are used to store data in a granular form i.e level of detail is more. The data in the infocube is in aggregated form.
from reporting point of view ods is used for operational reporting where as infocubes for multidimensional reporting.
ODS are used to merge data from one or more infosources but infocubes does not have that facility.
The default update type for an ODS object is overwrite for infocube it is addition. ODS are used to implement delta in BW. Data is loaded into the ODS object as new records or updating existing records in change log or overwrite existing records in active data table using 0record mode.
You cannot load data using Idoc transfer method in ODS but u can do in infocube.
you cannot create aggregate on ODS. you cannot create infosets on infocube.
ODS objects can be used
when u want to use the facility of overwrite.if u want to overwrite nonkey characteristics and key figures
If u want detailed reports u can use ODS.
If u want to merge data from two or more infosources you can use ODS.
IT allows u to drill down from infocube to ODS through RRI interface.
Moreover to conclude reporting performance wise cubes are better as compared to ODS.
As per your requirement you can have ur model with various advantages and disadvantages as mentioned above.
Note:all these information is availabe in various threads and if you would have checked thoroughly you would have got it.
With Regrads:
Prafulla Singh.
Edited by: prafulla singh on Mar 27, 2008 12:47 PM