ISYS114 Lecture Notes - Lecture 11: Distributed Database, Data Dictionary, Data Integrity

• School: Macquarie University
• Department: Information Systems
• Course: ISYS114
• Professor: Charanya

Document Summary

Dbms copy utility that produces backup copy of the entire database or subset. Cold backup database is shut down during backup. Hot backup selected portion is shut down and backed up at a given time. Audit trail of transactions and database updates. Transaction log record of essential data for each transaction processed against the database. Recovery manager dbms module that restores the database to a correct condition when a failure occurs and then resumes processing user requests. Disk mirroring switch between identical copies of databases. Restore/rerun reprocess transactions against the backup (only done as a last resort) Transaction integrity commit or abort all transaction changes. Forward recovery (roll forward) apply after images (preferable to restore/rerun) Co(cid:374)strai(cid:374)ts do(cid:374)"t (cid:272)ha(cid:374)ge fro(cid:373) (cid:271)efore tra(cid:374)sa(cid:272)tio(cid:374) to after transaction. Database changes not revealed to users until after transaction has completed. Problem in a multi-user environment, simultaneous access to data can result in interference and data loss (lost update problem)