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Use

The following update modes are available in the SAP BW (BW) scheduler:

  • 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:

  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, you can use the delta transfer for other master data attributes or texts.

To generate the control entry for master data attributes / texts necessary for SAP BW, proceed as follows:

  1. For an attribute or text DataSource, choose Start of the navigation path DataSource Next navigation step ALE Delta End of the navigation path.

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

    An F4 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. Apply 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.

Note

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 determine 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.

Note

The delta for generic DataSources cannot be used with a BW system release prior to 3.0. In older 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

  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:

    1. Enter a safety interval.

      The purpose of a security interval is to ensure that records that result from an extraction process but that could not be extracted are taken into account with the next extraction. This can occur, for example, if the records have not been saved.

      You can add a safety interval to the upper limit / lower limit of the interval.

      Caution

      For the lower limit, a safety interval only needs to be specified if the delta process has a new status for changed records, meaning if the status is overwritten in BW. In this case, duplicate data records that could arise in such a security interval have no affect on SAP BW.

    2. 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 SAP BW and into which data targets 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 in SAP BW. 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 SAP BW are overwritten. DataSources with this delta type can write data to DataStore objects and master data tables.

    3. 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.

Note

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

Safety 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 then: 12:00:00 to 12:28:00. At the end of the extraction, the pointer is set to 12:28:00.

Safety interval lower limit

The delta-relevant field is a timestamp. After images are transferred. That is, in SAP BW the record is overwritten with the status after the change, for example for master data. Any duplicate data records do not affect SAP BW.

The last read timestamp is 12:28:00. Delta extraction begins at 13:00. The safety interval for the lower limit is 180 seconds. The selection interval for the delta request is then: 12:25:00 to 13:00:00. At the end of the extraction, the pointer is set to 13:00:00.