Multi-level undo of main-memory and volatile resources

Abstract

System resources (e.g., objects or other resources) are managed to provide multiple levels of undo and/or support for delegation of updates on main-memory resident objects accessible by concurrent transactions. For example, a log associated with each transaction stores information regarding an update to an object when the object is locked in an update mode (e.g., a write mode) by the transaction. The transaction can be rolled back by restoring information from the log of the transaction to the object. If the transaction commits, then the log may be destroyed. If the transaction delegates to another transaction, the log of the transaction is also delegated. A record codelet can be automatically generated to perform the storing of information in the log, and a restore codelet can be automatically generated to undo updates by restoring information from the log to the updated objects. The codelets may be specific to each class of objects. Lock state information is used to identify undo information age so that the undo information may be stored in the log without regard to order, thereby enhancing the speed of the recording process.