The delta process is a feature of the extractor and specifies how data is to be transferred. As a DataSource attribute, it specifies how the DataSource data is passed on to the data target. From this you can derive, for example, for which data a DataSource is suited, and how the update and serialization are to be carried out.
The type of delta process affects the update into a data target. When you update data in an ODS object, you need to serialize it so that you can also overwrite it. According to the delta process, the system decides whether it is necessary to serialize by request or by data packet.
There are various delta processes for SAP source systems:
1. Forming deltas with after, before and reverse images that are updated directly in the delta queue; an after image shows the status after the change, a before image the status before the change with a negative sign and the reverse image also shows the negative sign next to the record while indicating it for deletion. This serializes the delta packets. The delta process controls whether adding or overwriting is permitted. In this case, adding and overwriting are permitted. This process supports an update in an ODS object as well as in an InfoCube. (technical name of the delta process in the system): ABR)
2. The extractor delivers additive deltas that are serialized by request. This serialization is necessary since the extractor within a request delivers each key once, and otherwise changes in the non-key fields are not copied over correctly. It only supports the addition of fields. It supports an update in an ODS object as well as in an InfoCube. This delta process is used by LIS DataSources. (technical name of the delta process in the system): ADD)
3. Forming deltas with after image, which are updated directly in the delta queue. This serializes data by packet since the same key can be copied more than once within a request. It does not support the direct update of data in an InfoCube. An ODS object must always be in operation when you update data in an InfoCube. For numeric key figures, for example, this process only supports overwriting and not adding, otherwise incorrect results would come about. It is used in FI-AP/AR for transferring line items, while the variation of the process, where the extractor can also send records with the deletion flag, is used in this capacity in BBP. (technical name of the delta process in the system): AIM/AIMD)
The field 0RECORDMODE determines whether the records are added to or overwritten. It determines how a record is updated in the delta process: A blank character signifies an after image, ‘X’ a before image, ‘D’ deletes the record and ‘R’ means a reverse image.
When you are loading flat files you have to select a suitable delta process from the transfer structure maintenance, this ensures that you use the correct type of update. You can find additional information under InfoSources with Flexible Updating of Flat Files.