Log Based Recovery
- The most widely used structure for recording database modification is the log.
- The log is a sequence of log records, recording all the update activities in the database.
- In short Transaction log is a journal, which contains history of all transaction performed.
- Log contains Start of transaction, trans-id, record-id, type of operation (insert, update, delete), old value, new value, End of transaction that is commit or aborted.
Techniques for recovery
Log Based Crash Recovery
Complete -> update
Change -> update