Compensation.java

/*

    - Class com.neocoretechs.arieslogger.logrecords.Compensation

   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF licenses this file to you under the Apache License, Version 2.0
   (the "License"); you may not use this file except in compliance with
   the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

 */

package com.neocoretechs.arieslogger.logrecords;

/**
	A Compensation operation can compensate for the action of a log operation.
	A Compensation operation itself is not undo-able, i.e., it is loggable but
	not undoable.
	The Compensation record 'logs' a non loggable operation by 'compensating' for a regular log record.
	The purpose is to track recover operations and limit the effect of repeated recoveries

	A Compensation operation is generated by the logging system when it calls
	undoable.generateUndo().  GenerateUndo should be the <B>only</B> way a 
	compensation operation can be made.
	http://www.cs.berkeley.edu/~brewer/cs262/Aries.pdf
	@see Undoable#generateUndo
*/
public interface Compensation extends Loggable {

	/**
	  Set up the undoable operation during recovery redo.

	  @param op the Undoable operation
	  @see Loggable#needsRedo
	*/
	public void setUndoOp(Undoable op);
}