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Recovery Facilities(1)
backup mechanism
- full or incremental
- store backup on offline storage
logging facilities
- DBMS maintains a special file called a log or journal contains info about all updates
- log contains:Transaction and checkpoint
records Fig. 22(20).25,may contain other info
for management
- maybe 2 or 3 copies,store on separated disk
- log file may be bottleneck of DBMS