SCO OpenServer 6, based on the merging of AT&T UNIX System V Release 4.2MP and UnixWare 7, was initially released by The SCO Group in 2005. It includes support for large files, increased memory, and multi-threaded kernel (light-weight processes). This merged codebase is referred to as UNIX System V Release 5 (SVR5) and was used only by SCO for OpenServer 6; SVR5 is not used by any other major developer or reseller. SCO OpenServer 6 contains the UnixWare 7's SVR5 kernel integrated with SCO OpenServer 5 application and binary compatibility, OpenServer 5 system administration, and OpenServer 5 user environments.