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write optimised DSO and PSA

Former Member
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Hi Gurus,

I have alittle doubt regarding the write optimised DSO.

Its understood that we r using this W-O DSO in the staging layer .( from Datasource (PSA)----> DSO). Its used for huge no of data and as it has only active table and no SID ... performencewise its good to have.. and also we need to delete the older data for the space in the DB table.

As the same thing we can get in the PSA. As data is also loaded on request level.. and we can delete after certain period of time say 7 days.... and to get historic data we can maintain a standard DSO with full load.

Then why to maintain WO-DSO in the staging layer

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naresh_babu3
Contributor
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Hi

PSA is staging layer, which contains no longer data, max 30 days, where as W-O DSO, u can keep for long time. it is also called as corporate layer.

1. you can create report on top of W-O DSO but u cant create report on top of PSA.

2. W-O DSO data is same as ECC data, we can reconsile here.

3. if u create report on top of W-O DSO then it is performance issue due to no indexs.

4. if u loss the data in Target u can easily extract the data from the W-O DSO in case of full upload, without distrubing the ECC System.

Write-optimized DSo is recommended in first layer because it contains active data table and noneed to activate DSO data seperately as it eases the task.Definitely u need to create transformations between datasource and this write-optimized DSO.Dtp is used load DTP between PSA and this write-optimized DSO.

Regards,

Naresh

christopherdcosta
Participant
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>

> Hi

>

> PSA is staging layer, which contains no longer data, max 30 days, where as W-O DSO, u can keep for long time. it is also called as corporate layer.

>

This comment is complete nonsense.

SAP Documentation clearly states that a Write Optimized DSO is technically the SAME as PSA in since version 7 of BI.

PSA in version BI7 is aligned now with the traditional notion of a Corporate Memory Layer whereby loaded data is kept in Persistent storage to enable a rebuild of data into the warehouse without referring back to the source systems which may have archived historic data already. It does not need to be duplicated into another storage area where again !

The name should already tell you that "Persistent" used in Persistent Staging Area means what it says and thankfully in BI7 SAP made it OBLIGATORY to pass through PSA - thereby effectively forcing you to at least think about what it means, even if you choose not to use it that way.

The question arises: why have a write optimized DSO then?

A: many companies feel "uncomfortable" not being able to actually see a persistent storage object in RSA1, and prior to it's creation many designers abused ODS (as they were then called) to behave like a corporate memory and take the role of PSA just for this reason alone. Unfortunately the standard ODS did not perform the same role because of the activation process which agregated the data and made it impossible to ,rebuild data exactly as it was sent.

The legacy of all this is that many designers wrongly assume that DSO is obligatory first layer in a datawarehouse and invoke Enterprise Datawarehousing as the justification, without really knowing what it means. What ends up happenning is that the Write Optimized DSO contains duplicate data from PSA, it adds an unnecessary layer of dataloading.

In their ignorance they overlook the real meaning of PSA. Rant over.

Edited by: Christopher DCosta on Mar 24, 2011 4:33 PM