As a rule of thumb, you should set CONTROL_FILE_RECORD_KEEP_TIME to several days
beyond your actual recovery window to ensure that backup records are retained in the control
file. The default is 7 days.
DB_RECOVERY_FILE_DEST
This parameter specifies the location of the flash recovery area. It should be located on a file
system different from any database datafiles, control files, or redo log files, online or archived. If
you lose the disk with the datafiles, the flash recovery area is gone too, mitigating the advantages
of using a flash recovery area.
DB_RECOVERY_FILE_DEST_SIZE
The parameter DB_RECOVERY_FILE_DEST_SIZE specifies an upper limit to the amount of space
used for the flash recovery area. The underlying file system may have less or more than this amount
Chapter 12: Using Recovery Manager (RMAN) 433
of space; the DBA should ensure that at least this amount of space is available for backups. Note
that this is the amount of recovery space for this database only; if multiple databases share the same
ASM disk group for their flash recovery area, the sum of all values for DB_RECOVERY_FILE_DEST_
SIZE must not exceed the available space in the disk group.
In our data warehouse database, dw, a flash recovery area is defined in the disk group +RECOV
with a maximum size of 8GB. As this limit is reached, RMAN will automatically remove obsolete
backups and generate an alert in the alert log when the amount of space occupied by nonobsolete
backups is within 10 percent of the value specified in DB_RECOVERY_FILE_DEST_SIZE.
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