(Glue-2108) BW Delta Mechanisms

Delta mechanisms (deltas) specify how the data is extracted. Currently, the BW delta functionality is supported only for the extraction from a SAP BW system to storage.

Deltas serve only as a data source definition and do not specify higher purpose processes like replication, offloading, etc. Based on the type of the extractor Glue executes the following BW delta types:

Change log delta

This delta reads data based on a Change log table of an InfoProvider. The initial full load reads data from the Active table of an InfoProvider. Then the delta is automatically initialized with activation request values currently available in the Change log table. Next load reads data from the Change log table, reading only records with activation request values that weren't loaded yet. That means only records with a new request values are transferred during the next execution of an extractor.

Delta properties

Properties tab contains general information about the extractor and the delta details:

• Delta type
• Status - actual status of the extractor (Saved or Active)
• Source - the name of a source InfoProvider
• Last extraction - date and time of the last extraction
• Full load - indicates whether a full load was executed

The Properties section shows

• Truncate target table - if you select this checkbox, all data in the target table is deleted before new extraction.

Set up values that will be exported from the Change log

Select at least one Record mode value which should be exported from the Change log table of the DSO. Record mode is a SAP functionality. You can find more information in the section "0RECORDMODE Values" of the blog Recordmode and delta type concepts.

_{Delta Tools - Properties tab}

Manage

In Manage you may execute data extractions.
Perform delta run executes a standard delta extraction.
Perform full load executes a full load even if it was already performed. By the first full load, the Change log delta is initialized. If you execute the full load repeatedly, the delta values won't be updated.
Reset delta value button resets delta value.

Request delta

Request delta reads data based on DTP requests loaded into an InfoProvider. During the initial full load, all data is read from an InfoProvider and the delta is initialized with the highest request value. Then the next load reads data with DTP request values greater than the current maximum. After this, the maximum DTP request value is updated to a new value.

Delta properties

Properties tab contains general information about the extractor and the delta details:

• Delta type
• Status - actual status of the extractor (Saved or Active)
• Source - the name of an InfoProvider
  
• Last extraction - date and time of the last extraction
• Full load - indicates whether the full load was executed

The Properties section shows

• Highest loaded value - Greatest loaded value of an InfoProvider DTP request.

Manage

Manage functionality isn't currently supported for the request-based delta extraction. 

0RECORDMODE Values: 

Technical flag with additional information about a particular record change log table.

Empty space : The record provides an after image. The status of the record is transferred after it has been changed or after data has been added.

X: The record provides a before image. The status of the record is transferred before it has been changed or deleted. All attributes for the record that can be aggregated (key figures) must be transferred with a reversed plus/minus sign. These records are ignored in a non-additive (overwriting) update of a DataStore object. The before image complements the after image.

A: The record provides an additive image. This provides the record with differences for all the numeric values that are available. The record can be updated to an InfoCube without restrictions but requires an additional update to be made to a DataStore object.

D: The record must be deleted. Only the key is transferred. This record (and therefore the DataSource too) can only be updated to a DataStore object.

N: The record provides a new image. The content of this record is equivalent to an after image without a before image. A new image should be transferred instead of an after image when a record is created. The new image complements the reverse image.

R: The record provides a reverse image. The content of this record is equivalent to a before image. The only difference occurs when updating a DataStore object: An existing record with the same key is deleted.

Y: Can only be updated to a DataStore object.