code: private boolean doesIndexExists(Connection con, String indexName) {
  
          if (usingDB2) {
              if (usingAS400DB2) {
                  return doesIndexExistsiSeries(con, indexName);
              }
              return doesIndexExistsDistributed(con, indexName);
          } else
              return false;
      }
docs: PK56991 we are checking if there is an existing index for the session table
  in distributed and iSeries platforms. The same test does not apply to zOS
  system as if we ask the customer to create the session index manually during
  table creation. Session manager does not create session index.