What must be implemented in an ABAP class for an ABAP Managed Database Procedure (AMDP)?

The correct answer requires implementing the interface IF_AMDP_MARKER_HDB in an ABAP class designed for an ABAP Managed Database Procedure (AMDP). This interface plays a crucial role in identifying that the class can contain AMDP methods, which directly interact with the database layer.

By implementing IF_AMDP_MARKER_HDB, the class is recognized by the ABAP runtime as intended for AMDP operations. This is essential because it ensures that the appropriate context and processing mechanisms are activated for any methods defined within that class, allowing them to execute SQLScript in the HANA database. This interface provides the necessary metadata that informs both the compiler and runtime about the capabilities of the class concerning database procedures.

The other options do not align with the requirements for defining AMDPs. Subclassing CL_AMDP_RUNTIME_HDB is not mandatory for AMDPs; it's designed for specific use cases and is not a general requirement. Setting the database visibility level to PRIVATE is relevant for encapsulation but does not define the class as an AMDP. Lastly, defining an event handler method is unrelated to AMDP and not necessary for their implementation.