Oldname

This option causes GAMS to only allow 10 character item set element names for compatibility with systems that do not accept longer names (notably older versions of MPSGE).  It causes GAMS to check that all set element names are less than 10 characters and uppercases the names.

Option Oldname=1;

When the set names are too long an execution error arises.  There is also an Note it does not require less than 10 character set, parameter, variable etc names and may still not work with older versions.