ABAP Core Data Services (CDS) is a still rather new data dictionary infrastructure that was introduced with SAP NetWeaver 7.40. It allows defining and consuming semantically rich data models.
Without CDS, intensive calculations are done on the application layer, avoiding costly computations in the database. This results in rather simple SQL queries between application and database layer. However, the drawback is that lots of data need to be transferred back and forth between those two layers. Often, this is very time-consuming.

CDS allows for a data centric approach. Intensive computations are pushed into the database by using complex views and functions. Depending on the use case, this may dramatically reduce execution time and simplify application coding.

The CDS framework was introduced to leverage the computational power of HANA DB. Nevertheless, it can also be used with all other databases that support SAP NetWeaver (anyDB).  The following database products supported for SAP NetWeaver are covered:
• IBM Db2 for i
• IBM Db2 for Linux, Unix and Windows
• IBM Db2 for z/OS
• Microsoft SQL Server
• Oracle Database
• SAP Adaptive Server Enterprise (SAP ASE)
• SAP MaxDB

ABAP Core Data Services on anyDB – Best Practice Guide has just been published. 

This guide gives hands-on information on how to implement, run and optimize CDS based applications on anyDB.  

Link:  https://tinyurl.com/SAP-ABAP-CDS-on-anyDB

Since CDS is a still rather new technology, this guide is “work in progress”, and it is expected that updates will be published twice a year.