An index that was created by a release of DB2 Universal Database for z/OS, Version 3, or earlier, or that was specified as a type-1 index in Version 4. A type-1 index is also an index that was created by a release of DB2 Universal Database for Linux, UNIX, and Windows, Version 7, or earlier, or that was specified as a type-1 index in Version 8, or later. See also type-2 index.