Once the ABAP handler interprets the business object data, the ABAP handler must integrate it with the SAP application database. It must manipulate the business object data to use SAP native APIs such as Call Transaction, BAPI, or ABAP SQL to get data into or out of the application database.
The intent of a Create, Update, or Delete operation is to modify the SAP application database. While the SAP application database schema for a given business object defines the structure of the data, the transactions provided by SAP that modify that data have a much broader scope of influence. As a result, directly modifying the application database tables of an SAP application can have disastrous results to the applications's data integrity.
Instead of directly modifying the database tables, SAP provides a flexible ABAP API (Call Transaction) for Create, Update, and Delete operations. Call Transaction is SAP-provided functionality for entering data into an SAP application. It guarantees that the data adheres to SAP's data model by using the same screens an online user would use in a transaction. This process is commonly referred to as screen scraping.
If the verb is Retrieve, then the connector uses ABAP SQL statements to retrieve data from the SAP application database. The business object data provides the keys for the where clause when pulling data. The difficulty in this methodology of retrieving data is that the retrieved data must be represented in a format that represents the business object structure. This is done in the ABAP handler ABAP code.