In the rapidly evolving world of information technology, the integration of established systems like mainframes with emerging paradigms such as the hybrid cloud represents a significant and challenging frontier. This book, 'Mainframes in the Hybrid Cloud Era,' is crafted to bridge the knowledge gap between these seemingly disparate worlds, providing a comprehensive guide to understanding, implementing, and optimizing mainframe systems within the hybrid cloud infrastructure. Mainframes have long been the backbone of critical business operations for many large organizations, known for their reliability, scalability, and security. However, as cloud computing has risen to prominence, bringing flexibility, cost-efficiency, and innovative capabilities, a crucial question has emerged: How can the robustness of mainframes be harmoniously combined with the agility of cloud environments? This book aims to answer this question, presenting a balanced view that respects the legacy of mainframes while embracing the future of cloud technologies. Throughout the chapters, we explore various facets of this integration. From the architectural considerations of combining mainframes with cloud infrastructures to the specific challenges of data management, security, and application development in a hybrid environment, the book covers a broad spectrum of topics. Each chapter is designed to provide practical insights and actionable strategies, drawn from real-world experiences and current best practices. Moreover, this book does not merely focus on the technical aspects. It also delves into the strategic and managerial perspectives, crucial for leaders and decision-makers who need to navigate the complexities of integrating mainframe systems with cloud solutions. By providing a range of case studies and future-looking predictions, the book offers a comprehensive view of the field, beneficial for both technical professionals and business leaders. As the author, my intention is to provide a resource that is not only informative but also accessible to a wide range of readers. Whether you are a seasoned IT professional, a student of information technology, or a business leader seeking to understand the implications of mainframe and cloud integrations, this book is for you. It is my hope that 'Mainframes in the Hybrid Cloud Era' will serve as a valuable guide and reference as you navigate the exciting and challenging world of mainframe and hybrid cloud computing.