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Physical Backups  «Prev 

Advantages and Disadvantages for Closed Database Backup

ADVANTAGES DISADVANTAGES
Maintain high database availability -
When using an open database backup, the database is available for process access during the backup and the business transactions will not be interrupted because of the backup.
More training required for the DBA -
Because an open database backup is a complicated process (compared to the closed database backup), a DBA will need more training to handle the process.
Can be done at a tablespace or datafile level -
A DBA may choose to backup all the datafiles for a specific tablespace or just individual datafiles for a tablespace.
More error-prone -
An online database backup is more error-prone because of additional operator interaction. Thus, it is best to use tested scripts to automate the process.
Allows recovery to point-in-time -
With an open database backup, the DBA may choose to recover the database to a certain point of time.
 

Online Redo Log Switching

Another important RMAN feature is automatic online redo log switching. To make an open database backup of archived redo logs that includes the most recent online redo log, you can execute the BACKUP command with any of the following clauses:
  1. PLUS ARCHIVELOG
  2. ARCHIVELOG ALL
  3. ARCHIVELOG FROM
Before beginning the backup, RMAN switches out of the current redo log group, and archives all online redo logs that have not yet been archived, up to and including the redo log group that was current when the command was issued. This feature ensures that the backup contains all redo generated before the start of the command.
An effective way of backing up archived redo logs is the
BACKUP ... PLUS ARCHIVELOG
command, which causes RMAN to do the following:
  1. Runs the ALTER SYSTEM ARCHIVE LOG CURRENT statement.
  2. Runs BACKUP ARCHIVELOG ALL. If backup optimization is enabled, then RMAN skips logs that it has already backed up to the specified device.
  3. Backs up the rest of the files specified in the BACKUP command.
  4. Runs the ALTER SYSTEM ARCHIVE LOG CURRENT statement.
  5. Backs up any remaining archived logs generated during the backup. If backup optimization is not enabled, then RMAN backs up the logs generated in Step 1 plus all the logs generated during the backup.
  6. The preceding steps guarantee that data file backups taken during the command are recoverable to a consistent state. Furthermore, unless the online redo log is archived at the end of the backup, DUPLICATE is not possible with the backup.