Oracle Backup and Recovery Question

21. What are the architectural components of RMAN?
  Following are the architectural components of RMAN:
  • RMAN executable
  • Server processes
  • Channels
  • Target database
  • Recovery catalog database
  • Media management layer
  • Backups, backup sets and backup pieces
 
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22. Why is the catalog optional?
 
  • Catalog is optional because RMAN manages backup and recovery operations and it requires a place to store necessary information about the database.
  • RMAN always stores this information in the target database control file.
  • You can also store the RMAN metadata in a recovery catalog schema contained in a separate database.
  • The recovery catalog schema must be stored in a database other than the target database.
 
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23. How does RMAN improve performance of backup?
  RMAN uses multiple channels and does not take backup of free blocks. This is the reason why performance of RMAN backup is better.
 
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24. Why more redo is generated during hot backup?
 
  • During the hot backup, when a tablespace is put up in the backup mode, all the datafiles that belongs to the tablespace get their checkpoint frozen.
  • When DWBR process writes the changed data blocks to the datafile, the same data blocks are written to redo log files to hot backup.
  • This is the reason for large redo generation and requirement of archive logs for hot backup.
 
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