About Us

Virtual Software Systems, Inc. –  Home of VPARS, VTAPE, & ShadowDisk/Z

VSSI was formed in 1978 to develop extensions to the IBM VM operating system for the purpose of supporting the Transaction Processing Facility (TPF), an IBM system widely used by the travel, hospitality, and financial service industries. The first product developed was the Virtual Programmed Airline Reservation System (VPARS), a shadow database facility which allowed developers to code and test TPF programs using a shared database system under VM.

In 1982, VSSI began work of the development of a Dummy Tape (DTAPE) product in order to address the needs of the TPF community. After many enhancement requests from VPARS users, VSSI developed a more robust tape product (Virtual Tape or VTAPE), which provided full tape device emulation to VM users. Like VPARS, VTAPE utilizes a shared database which provides tape emulation support to hundreds of concurrent users in a single z/VM image.

VSSI has continually enhanced the VPARS and VTAPE products over time in order to maintain support through various IBM system enhancements (on the VM side, currently z/VM; on the TPF side, currently z/TPF). As a result, the products continue to enjoy wide acceptance and enhanced reliability, coupled with prompt and professional 24×7 support.

During the 2014 time frame, VSSI began work on a z/Linux product, ShadowDisk/Z. ShadowDisk/Z does for z/Linux users what VPARS does for z/TPF users; i.e., it provides a robust developer tool for the testing, and deployment of z/Linux applications via use of a shared database, thus saving users a significant amount of data storage hardware cost.