Message Oracle PLS-00493 - invalid reference to a server-side object or function in a local context

ERRORinvalid reference to a server-side object or function in a local context
CAUSEA reference to a server-side object (e.g. a table column) or function (a group function such as SUM, AVG, MIN, MAX, ... ) was found in a context where only PL/SQL objects may be present (such as within the parameter list of a local function or as the index of a (local) PL/SQL table.)
ACTIONRewrite the offending statement; or (if a local function call is the problem context), make the function non-local (either packaged or top- level.)