Databases Reference
In-Depth Information
• Complete database recovery to the point of failure
• Time-based or point-in-time database recovery (recovery of the entire database to
a time before the most current time)
• Tablespace point-in-time recovery (recovery of a tablespace to a time different from
the rest of the database)
• Recovery of individual tables (a new feature in Oracle Database 12
c
)
• Backup and recovery of multitenant container databases including backup and
point-in-time recovery of individual pluggable databases (new in Oracle Database
12
c
)
• Recovery until the
CANCEL
command is issued
• Change-based or log sequence recovery (to a specified System Change Number, or
SCN)
You can recover through RMAN, using either the recovery catalog or control file or via
SQL or SQL*Plus.
RMAN also supports the backup and restore of standby control files, has the ability to
automatically retry a failed backup or restore operation, and can automatically create
and recover Oracle datafiles not in the most recent backup. Where backups are missing
or corrupt during the restore process, RMAN automatically uses an older backup.
To speed backups and restore operations, the Flash Recovery Area, featured in the Ora‐
cle Database since Oracle Database 10
g
, organizes recovery files to a specific area on
disk. These files include a copy of the control file, archived logfiles, flashback database
logs, datafile copies, and RMAN backups. You can set a RETENTION AREA parameter
to retain needed recovery files for specific time windows. As backup files and archive
logs age beyond the time window, they are automatically deleted. ASM (described earlier
in this chapter) can configure the Flash Recovery Area. If availability of disk space is an
issue, you can also take advantage of RMAN's ability to compress backup sets.
Making Sure the Backup Works
The key to providing an adequate backup and recovery strategy is to simulate recovery
from failure using the backups with your test system before using the backups to restore
a live production database. Many times, backup media that were thought to be reliable
prove not to be, or backup frequencies that were thought to be adequate prove to be too
infrequent to allow for timely recoveries. It's far better to discover that recovery is slow
or impossible in test situations than after your business has been affected by the failure
of a production system.
