code: public LogSeqNum logSetVal(Buffer buff, int offset, Constant newVal) {
  		if (enableLogging) {
  			BlockId blk = buff.block();
  			if (isTempBlock(blk))
  				return null;
  			return new SetValueRecord(txNum, blk, offset, buff.getVal(offset, newVal.getType()), newVal).writeToLog();
  		} else
  			return null;
  	}
docs: Writes a set value record to the log.
  
  @param buff
  the buffer containing the page
  @param offset
  the offset of the value in the page
  @param newVal
  the value to be written
  @return the LSN of the log record, or -1 if updates to temporary files