Resolving The Problem

LONG may be a suitable replacement datatype. The LONG type will support data sizes in the Gigabyte range.  The LONG parameter can then be converted and processed by the stored procedure as a CLOB type.  

The following PL/SQL code shows how this could be done:

CREATE TABLE clobtest (x int, y clob);

CREATE OR REPLACE PROCEDURE   pclobtest( nID int, lArg LONG ) AS                 
  cPart  VARCHAR2(32767);
  cTest  CLOB;
  nLen   NUMBER;
  nTot   NUMBER;
  done   BOOLEAN;
BEGIN                                     
  DBMS_LOB.CREATETEMPORARY(cTest, false);
  
  IF lArg IS NOT NULL THEN
    nLen := length(lArg);
    nTot := 1;
    done := false;
  ELSE
    nLen := -1;
    nTot := -1;
    done := true;
  END IF;
  
  WHILE NOT done LOOP
    IF nTot <= nLen THEN
      cPart := substr( lArg, nTot, 32767 );
      nTot  := nTot + 32767;
      DBMS_LOB.WRITEAPPEND(cTest, length(cPart), cPart);
    ELSE
      done := true;
    END IF;
  END LOOP;
  
  IF nLen >= 0 THEN
    insert into clobtest values (nID, cTest);
  ELSE
    insert into clobtest values (nID, NULL);
  END IF;
  
  DBMS_LOB.FREETEMPORARY(cTest);
END;
/