Delta Transfer to BI 

The following update modes are available in BI:

●      Full update

A full update requests all data that meets the selection criteria you set in the scheduler.

●      Delta update

A delta update only requests data that has appeared in the source system since the last load.

●      Initializing the delta process

You need to initialize a delta process before you can execute it. The initialization selections are copied to load the delta records.

With large volumes of data, you can only ensure a performance-optimized extraction from the source system if you use a delta process.

In the maintenance of the generic DataSource, you can set up a delta for master data attributes and texts. You can also set up a generic delta using a (delta-relevant) field with a monotonically increasing value.

Setting Up an ALE Delta for Master Data Attributes or Texts

Master data attributes or texts for which you want to use a delta transfer have to fulfill two prerequisites:

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       1.      Data must be extracted generically using a transparent table or database view.

       2.      A change document object must be available that can update the complete key of the table (or view) used for data extraction in combination with one of the tables on which the change document object is based.

The required control entries are delivered for the most important master data attributes and texts. By including a maintenance interface for control entries in the maintenance of generic DataSources or InfoSources, you can use the delta transfer for other master data attributes or texts.

To generate the control entry for master data attributes or texts that is required for BI, proceed as follows:

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       1.      For an attribute or text DataSource, choose DataSource → ALE Delta.

       2.      Enter the table and the change document object that you want to use as a basis for the delta transfer.

An input help for the Table Name field searches all possible tables for a suitable key.

       3.      Confirm your entries.

If you have entered a usable combination of table and change document object, the extraction structure fields are listed in the table below. The status in the first column shows whether changing the master data in this field causes the system to transfer the delta record.

       4.      Save the settings to generate the required control entry.

Delta transfer is now possible for master data and texts.

After the DataSource has been generated, you can see this on the DataSource: Edit Customer Version screen; the Delta Update field is selected.

You need two separate entries if you want to transfer delta records for texts and master data attributes.

Generic Delta

If a field exists in the extraction structure of a DataSource and the field contains values that increase monotonically over time, you can define delta capability for this DataSource. If a delta-relevant field of this type exists in the extraction structure (a timestamp, for example), the system determines the data volume transferred in the delta mode by comparing the maximum value transferred with the last load with the amount of data that has since entered the system. Only the new data is transferred.

To get the delta, generic delta management translates the update mode into a selection criterion. The selections of the request are enhanced with an interval for the delta-relevant field. The lower limit of the interval is taken from the previous extraction. The upper limit is taken from the current value, for example, the timestamp at the time of extraction. You use security intervals to ensure that all data is taken into account during extraction (see below). After the data request is transferred to the extractor and the data is extracted, the extractor informs generic delta management that the pointer can be set to the upper limit of the previously determined interval.

The delta for generic DataSources cannot be used with a BI system release prior to 3.0. In older SAP BW releases, the system does not replicate DataSources for master data and texts that were delta-enabled using the delta for generic DataSources.

Determining Generic Delta for a DataSource

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       1.      Choose Generic Delta.

       2.      In the dialog box that appears, specify the delta-determining field and the type of this field.

       3.      Maintain the settings for the generic delta:

                            a.      Enter a security interval.

The purpose of a security interval is to make the system extract records with the next extraction that appear during the extraction process but which have not yet been extracted (because, for example, they have not been saved).

You can add a security interval to the upper limit or lower limit of the interval.

You should only specify a security interval for the lower limit if the delta process produces a new status for the changed records (when the status is overwritten in BI). In this case, duplicate data records that may arise with a security interval of this type have no affect in BI.

                            b.      Choose the delta type for the data that you want to extract.

You use the delta type to determine how the extracted data is interpreted in BI and the data targets to which it can be updated.

With the Additive Delta delta type, the record to be loaded for cumulative key figures only returns the change to the respective key figure. The extracted data is added into BI. DataSources with this delta type can write data to DataStore objects and InfoCubes.

With the New Status for Changed Records delta type, each record to be loaded returns the new status for all key figures and characteristics. The values in BI are overwritten. DataSources with this delta type can write data to DataStore objects and master data tables.

                            c.      Specify whether the DataSource supports real-time data acquisition.

       4.      Save your entries.

Delta transfer is now possible for this DataSource.

After the DataSource has been generated, you can see this on the DataSource: Edit Customer Version screen; the Delta Update field is selected.

In systems as of Basis Release 4.0B, you can display the current value of the delta-relevant field in the delta queue.

Example of Determining Selection Intervals with Generic Delta

Security interval upper limit

The delta-relevant field is a timestamp.

The timestamp that was read last is 12:00:00. Delta extraction begins at 12:30:00. The security interval for the upper limit is 120 seconds. The selection interval for the delta request is: 12:00:00 to 12:28:00. When the extraction is finished, the pointer is set to 12:28:00.

Security interval lower limit

The delta-relevant field is a timestamp. After images are transferred. In BI the record is overwritten with the post-change status, for example, for master data. Any duplicate data records do not affect BI.

The last read timestamp is 12:28:00. Delta extraction begins at 13:00. The security interval for the lower limit is 180 seconds. The selection interval for the delta request is: 12:25:00 to 13:00:00. When the extraction is finished, the pointer is set to 13:00:00.