Triggering a Delta Merge

If you are using an SAP HANA database, data modifications are initially saved in a delta storage that is optimized for write access. The modifications then have to be transferred to the main storage by means of a delta merge.

Data modifcations are initially stored in the database in a delta storage optimized for write access. Most of the data is saved in a highly compressed format in the main storage however, which is optimized in terms of required memory space and read performance. A delta merge is used to transfer modifications from the delta storage to the main storage. First, an asynchronous check is performed for see whether a delta merge is required. If a threshold value is exceeded, the merge is carried out in the delta storage. When a read access is executed, the data is read from the main storage and the delta storage and the results are merged together.

Note This function is not relevant for objects whose tables are generated as extended tables. More information: SAP HANA SAP HANA Dynamic Tiering for Using Extended Tables

The check and the delta merge - if data has been changed during Data Warehouse load processes - are either performed automatically by the system or must be triggered manually. This depends on the relevant object type:

After activation for standard DataStore objects (classic), an automatic check is run in order to ascertain out whether a delta merge can be performed. This also applies to DataStore objects that belong to a semantically partitioned object.
After data has been written to the PSA for DataSources, an automatic check is run in order to ascertain whether a delta merge can be performed.
For write-optimized DataStore objects (classic), standard InfoCubes and SAP HANA-optimized InfoCubes, the check and the delta merge (if possible) are not performed automatically. This also applies to objects that belong to a semantically partitioned object.

The data transfer process (DTP) has an Update tab that contains the Trigger Database Merge checkbox. This controls the delta merge, once the DTP request has been successfully processed. This checkbox is selected in the default setting.
For DataStore objects (advanced), the Trigger Database Merge checkbox is also selected by default. After activation, an automatic check is run in order to ascertain out whether a delta merge can be performed.

Note In certain exceptional cases, performing a delta merge after processing a DTP request is not recommended, due to load balancing issues. You can only use a process type in exceptional situations like this.