Backup and Recovery Flashcards
How would you decide you backup strategy and timing for backup?
An optimal backup strategy depends heavily on the client’s or company SLA. There are three areas to take take into consideration. They are the frequency of DB availability, length of downtime following a crash or failure, and the amount of data loss tolerated.
What is the difference between restoring and recovering the database?
Restoring is copying backup files from secondary storage to the disk. This is often done to replace damaged files or to copy/move a database to a new location. Recovery is the process of applying redo logs to the database to roll it forward. The DB can roll forward until a specific point in time or until the last transaction recorded in the log files.
What is the difference between complete and incomplete recovery?
- Complete recovery uses redo data or incremental backups combined with a backup of a database, tbs, or datafile to update it to the most current point in time.
- Incomplete recovery uses a backup to produce a concurrent version of the database. The redo records generated after the most recent backup aren’t applied.
What is the benefit of running the DB in archive log mode over noarchivelog mode?
Noarchivelog mode protects against instance failure but not against media failure. If media failure occurs, you can only restore the most recent backup. You also cannot perform online table space backups. Archivelog mode ensures that you can recover all committed transactions in the event of a system or disk failure.
What is the difference between Hot Backup and RMAN?
An RMAN backup will backup the entire database up until that point in time. It will backup the physical blocks as well as the DB archive logs which will provide recovery options. A hot backup is taken while the DB is still online which can result in inconsistencies if users still have access and are making changes during the backup.
Why RMAN incremental backups fail even though full backup exists?
If you have taken an RMAN backup using the command “Backup Database”, it is not recorded in the RMAN repository as an incremental backup thus it cannot be used for a level 1 backup.
