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Tuesday, April 6, 2010

How much FAST RECOVERY AREA?

use the following formula to estimate the disk quota, where n is the interval in days
between incremental updates and y is the delay in applying the foreign archived redo
logs on a logical standby database:

Disk Quota =
Size of a copy of database +
Size of an incremental backup +
Size of (n+1) days of archived redo logs +
Size of (y+1) days of foreign archived redo logs (for logical standby) +
Size of control file +
Size of an online redo log member * number of log groups +
Size of flashback logs (based on DB_FLASHBACK_RETENTION_TARGET value)


To determine the optimum size for the fast recovery area:
1. If you plan to use flashback logging or guaranteed restore points, then query
V$ARCHIVED_LOG to determine how much redo the database generates in the
time to which you intend to set DB_FLASHBACK_RETENTION_TARGET.


If flashback logging is enabled, then run the database under a normal workload
for the time period specified by DB_FLASHBACK_RETENTION_TARGET.
In this way, the database can generate a representative sample of flashback logs.

Query the V$FLASHBACK_DATABASE_LOG view as follows:
SELECT ESTIMATED_FLASHBACK_SIZE
FROM V$FLASHBACK_DATABASE_LOG;

The result is an estimate of the disk space needed to meet the current flashback
retention target, based on the database workload since Flashback Database was
enabled.


Oracle recommends that DB_RECOVERY_FILE_DEST be set to a different value from
DB_CREATE_FILE_DEST or any of the DB_CREATE_ONLINE_LOG_DEST_n
initialization parameters.

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