About Global Temporary Table and Stored Procedure in Oracle
GLOBAL TEMPORARY
  
  Specify GLOBAL TEMPORARY to indicate that the table is temporary and
  that its definition is visible to all sessions with appropriate
  privileges. The data in a temporary table is visible only to the
  session that inserts the data into the table.


http://docs.oracle.com/database/121/SQLRF/statements_7002.htm#SQLRF01402