line item dimension

[Former Member]

Hi,

why we cerate line item dimension........

at what secnario we going to create............

how to create...............

expalin me...............

[Former Member]

Hi

refer to the below link for more detail on line item dimention

http://help.sap.com/saphelp_nw04/helpdata/en/e3/e60138fede083de10000009b38f8cf/frameset.htm

When compared to a fact table, dimensions ideally have a small cardinality. However, there is an exception to this rule. For example, there are InfoCubes in which a characteristic document is used, in which case almost every entry in the fact table is assigned to a different document. This means that the dimension (or the associated dimension table) has almost as many entries as the fact table itself. We refer here to a degenerated dimension. In BW 2.0, this was also known as a line item dimension, in which case the characteristic responsible for the high cardinality was seen as a line item. Generally, relational and multi-dimensional database systems have problems to efficiently process such dimensions. You can use the indicators line item and high cardinality to execute the following optimizations:

...

1. Line item: This means the dimension contains precisely one characteristic. This means that the system does not create a dimension table. Instead, the SID table of the characteristic takes on the role of dimension table. Removing the dimension table has the following advantages:

¡ When loading transaction data, no IDs are generated for the entries in the dimension table. This number range operation can compromise performance precisely in the case where a degenerated dimension is involved.

¡ A table- having a very large cardinality- is removed from the star schema. As a result, the SQL-based queries are simpler. In many cases, the database optimizer can choose better execution plans.

Nevertheless, it also has a disadvantage: A dimension marked as a line item cannot subsequently include additional characteristics. This is only possible with normal dimensions.

2. High cardinality: This means that the dimension is to have a large number of instances (that is, a high cardinality). This information is used to carry out optimizations on a physical level in depending on the database platform. Different index types are used than is normally the case. A general rule is that a dimension has a high cardinality when the number of dimension entries is at least 20% of the fact table entries. If you are unsure, do not select a dimension having high cardinality.

[Former Member]

Hi,

you can check in RSRV in database -> "Display database information about tables" and execute test.

In the log you will see how much percentage the dimensions take in relation to fact table. Recommended ist to have about max. 30%, otherwise database access to this diemnsion is slow. Also your load process gets slower (in the request monitor look at update). It takes long time because the SID generation takes a long time. To reduce this time, SAP recommends to build so called line item dimensions. In line items only one characteristic is in the dimension and it is expteted to have lots of entries in relation to fact table. 0MATERIAL is a typical candidate. How to create a line item dimension? Gotto cube->change->goto the dimension, right mouse and properties. Here you have the options line item and high cardinality. If you have only one characteristic in your dimension you can check line item dimension. But if yiu have data in your cube, you can'T chanfe. First you have to delete all data and then you can mark the dimension as line item.

Line items are only for cubes, not for DSO or mutliprovider!

Thechnically with line items ,the facttabel will be joined directly with the sId table of your characteristic. Otherwise you have the dim table with dimid as key and the sids of your characterisitcs in the dimension. So database has to make bigger Joins over more tables. So you see, make small dimensions as posible, use all 12 free dimensions and don'T create your dimensions for business reasons. This you can do in Multiprovider!

Regards,

Juergen

[Former Member]

Line item Dimension is created in cases where the dimension data is growing 20 percent that of the fact table.then we go for line item to reduce the one join.

for ilustration u can take the orderno where we go for a line item .

But the thing is we only need to have a single characterstic in the line item dimension

Regards

<b>Sarvepalli</b>

[Former Member]

Hi Lakshmi,

Generally we go for line item dimension when data records are unique, like document no.Document no is unique, in this type of cases more no of dimids are generated.so dimension table size would be more.

you have go for line item dimension when dimension table size is > 30% of the fact tbale.

Assign points if it is useful.

Regards

Prasad

[former_member584159]

Hi,

to add some more points to above post... go throught his post..

Regards,

Senthil

[Former Member]

Hi Lakshmi,

You can create a line item dimension if you have only one characteristic in the dimension. What this does technically is that instead of putting the DIMID as a foreign key in the fact table it will put the SID of the characteristic as a foreign key.

This will result in one less join at query execution time and hence improved query performance.

To create a line item dimension just right click on the dimension and click on properties. Check the 'Line item dimension' checkbox. Hope this helps. Thanks.

Sumit