SQL/DS (Structured Query Language/Data System) was IBM's first commercial implementation for its mainframe computers of a DBMS (Database Management System) built around the SQL language.
SQL/DS is an (imperfect) software implementation of Dr. E. F. Codd's Relational Model for data management.
SQL/DS ran on the DOS/VSE and VM/CMS operating systems. It came to market in the early 1980s. A little later, IBM also introduced DB2, another SQL-based DBMS, this one for the MVS operating system. The two products have coexisted since then; however, SQL/DS was rebranded as "DB2 for VM and VSE" in the late 1990s.