2数据库备份方法.ppt

Phases of Instance Recovery Data files out-of-sync Roll forward (redo) Committed and non-committed data in files Roll back (undo) Committed data in files Database Undo Instance SGA 146.5 Background Processes Data File SCN: 99 Data File SCN: 129 Data File SCN: 140 Control File SCN: 143 Control File SCN: 143 Redo Log Group SCN 74-101 Redo Log Group SCN 102-143 lab3 Tuning Instance Recovery During instance recovery the transactions between the checkpoint position and end of redo log must be applied to the data files. Tune instance recovery by controlling the difference between the checkpoint position and end of redo log. End of redo log Checkpoint position Transactions Instance recovery Configuring for Recoverability To configure your database for maximum recoverability: Schedule regular backups Multiplex control files Multiplex redo log groups Retain archived copies of redo logs Control Files Protect against database failure by multiplexing control files. At least two copies (Oracle suggests three) Each copy on a separate disk At least one copy on a separate disk controller Control Files Redo Log Files Multiplexing redo log groups to protect against media failure and loss of data. At least two members (files) per group Each member on a separate disk drive Each member on a separate disk controller Redo logs heavily influence performance Group 1 Group 2 Group 3 Member 1 Member 2 Member 1 Member 2 Member 1 Member 2 Disk 1 Disk 2 Multiplexing the Redo Log Archived Log Files To preserve redo information, create archived copies of redo log files. Specify archived log file naming convention. Specify one or more locations to archive logs to. Switch the database to ARCHIVELOG mode. Online Redo Log Files Archived log files Archive Log File Naming and Destinations Specify archived log file name and destinations. ARCHIVELOG Mode Place the database in ARCHIVELOG mode. Click the ARCHIVELOG Mode checkbox Click Apply. The database can only be set to ARCHIVELOG mode from the MOUN