docs: public final void setTransactionIsolation(int isoLevel) throws SQLException 
      {
          if (currentTransactionIsolation != isoLevel) {            
              // Reject switching to an isolation level of TRANSACTION_NONE
              if (isoLevel == Connection.TRANSACTION_NONE) {
                      throw new SQLException(AdapterUtil.getNLSMessage("DSRA4011.tran.none.iso.switch.unsupported", dsConfig.get().id));
              }
              
              if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) 
                  Tr.debug(this, tc, "Set Isolation Level to " + AdapterUtil.getIsolationLevelString(isoLevel));
              
              // Don't update the isolation level until AFTER the operation completes
              // succesfully on the underlying Connection. 
              
              sqlConn.setTransactionIsolation(isoLevel); 
              currentTransactionIsolation = isoLevel; 
              isolationChanged = true; 
          }
          if (cachedConnection != null) 
              cachedConnection.setCurrentTransactionIsolation(currentTransactionIsolation, key);
      }