Hi Chris,
A few comments.
Export:
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First of all, today, where 24x7 is a requirement, EXP and IMP are not backup and recovery tool at all. They are relatively simple tools that should be used to move a modest amount of data back and forth between instances, or, by using transportable tablespaces, to move massive amounts of data. To use it to backup a 500GB database would be ludicrous.
Offline backup:
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Copying of the datafiles, control file and online redo log files must be done by using an operating system copy utility. This is a considered as a complete backup of the database. Any changes made after this backup will be unrecoverable if the database is running in NOARCHIVELOG mode. All transactions are recorded in online redo log files whether archiving or not. When redo logs are archived (ARCHIVELOG mode), ORACLE allows you to apply these transactions after restoring files that were damaged (assuming an active Redo log file was not among the files damaged).
Online backup:
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A database backup, together with online and archived redo log files, guarantees that you can recover all committed transactions in the event of an operating system or disk failure.
You can use a backup taken while the database is open and in normal system use if you keep an archived log.
At sites where a database must operate 24-hours per day and when it is not feasible to take offline backups, then an alternative is provided by Oracle where physical backups are performed while the database remains available for both reading and updating. For this kind of backup the database must be in ARCHIVELOG mode. Only data files and current control file need to be backed up. Unlike offline backups, the unit of a online backup is a tablespace, and any or all tablespaces can backed up whenever needed. Different datafiles can be backed up at different times.
In general for Media Recovery using archived log, the following applies:
Manual recovery after media failure enables you to control how many redo log files to apply to the database. This can used to undo an inadvertent change to the database by stopping recovery before the change took place. MANUAL option needed for recovery with a control file backup (old copy) and current control file is not available. Database must be MOUNTed but not OPEN. After MOUNTing the database connect internal and issue RECOVER DATABASE MANUAL command. Then you will be prompted beginning with the earliest redo log file recorded in the header of each database file. The recovery process will continue to prompt for redo log files until CANCEL is typed when prompted for the next redo log file. Recovery can be cancelled at any time of any redo log.
How to apply ARCHIVED LOGS on an OFFLINE BACKUP
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Datafiles should have information of log change nbr (SCN), so Oracle knows which archived logs need to be applied to get DB on date. This can be done "usually":
- alter database mount
- recover database until cancel
- alter database open [resetlogs] (if uncomplete recovery)
If you need any further clarifications please let us know.
Hope this helps!
Best Regards
Yogeeraj
No person was ever honoured for what he received. Honour has been the reward for what he gave (clavin coolidge)
