Question

Discuss how the ARIES algorithm must operate under the circumstances that the system crashes during recovery

Answer 1

ARIES stands for Algorithm for Recovery and Isolation Exploiting Scmantics.ARIES uses logs to record the progress of transactions and their actions which cause changes to recoverable data objects. The log is the source of truth and is used to ensure that committed actions are reflected in the database, and that uncommitned actions are undone. Conceptually the log is a single ever-growing sequential file (append-only). Every log record has a unique log sequence number (LSN), and LSNs are assigned in ascending order.

Log records contains Redo and Undo information. Redo records contains after changes of transaction. Redo is used if the data is lost in between the transaction.and Undo is used to do the rollback of the transaction.

These all the Redo and Undo operations on the log can be used to recover data when system crashes.the data can be retain back by using ARIES algorithm with these operations.