Mainframe is used for hosting large commercial databases, transaction servers and applications that require a greater degree of reliability, scalability and security. Customer Information Control System (CICS) is a mainframe software framework for implementing transaction services. It is designed for rapid, high-volume online processing. In order to design, develop and test new functionalities and enhancements to the existing software applications running on the mainframe, each project requires a separate CICS development region. There is a huge cost associated with the degree to which the various components of the mainframe CICS infrastructure can be expended. Other related costs incurred are the maintenance fees and support expenses. This basically limits the ability of an organization to expand their infrastructure frequently, and hence the amount of development work is limited to what their existing mainframe CICS resources can support. This study attempts to support the development work for multiple new or enhancement projects in a single CICS region without compromising the integrity of the code. We present a unique method to create several instances of "virtual" regions within a single CICS region where each of the virtual ones uses its own versions of programs and files or common programs and files. "RACF", an IBM security controls program that provides access controls and auditing on the dedicated CICS region, can be applied to the virtual regions along with the "CICS authorization security." This solution has been tested with successful results and would enable mainframe-CICS users to develop multiple development initiatives concurrently within a single physical CICS region, hence the proposed methodology not only improve the use of existing infrastructure without incurring significant expenses but also maintain the data integrity as well. The method is validated by a series of experiments for the functions, security, and system resource usages. The experiments show that the proposed method follows the basic operational principles of CICS and the creation of several instances of virtual regions would enable the mainframe users to support multiple development initiatives without expanding on their existing infrastructure. A survey with select mainframe domain experts also confirms that the method is practical, efficient and important in enabling the mainframe users to perform concurrent development work for several projects in a single CICS region. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]