Database Reference
In-Depth Information
RMAN works fine with or without a recovery catalog. For several of the databases I maintain, I don't use a
recovery catalog; this eliminates having to set it up and maintain it. For me, simplicity takes precedence over the
features available with the recovery catalog.
However, if you have good business reasons for using a recovery catalog, then implement and use one. The
recovery catalog isn't that difficult to set up and maintain, and Oracle recommends that you use it.
11. Using a Media Manager
A media manager is required for RMAN to back up directly to tape. Several vendors provide this feature (for a cost).
Media managers are used in large database environments, such as data warehouses, in which you may not have
enough room to back up a database to disk. You may also have a disaster recovery requirement to back up directly
to tape.
If you have such requirements, then you should purchase a media management package and implement it. If you
don't need to back up directly to tape, there's no need to implement a media manager. RMAN works fine backing up
directly to disk.
Keep in mind that many shops use RMAN to back up directly to disk and then have the system administrator
back up the RMAN backups to tape afterward. If you do this, you have to be sure your RMAN backups aren't running
while the tape backups are running (because you may get partial files backed up to tape).
12. Setting the CONTROL_FILE_RECORD_KEEP_TIME
Initialization Parameter
The
CONTROL_FILE_RECORD_KEEP_TIME
initialization parameter specifies the minimum number of days a reusable
record in the control file is retained before the record can be overwritten. The RMAN metadata are stored in the
reusable section of the control file and therefore are eventually overwritten.
If you're using a recovery catalog, then you don't need to worry about this parameter because RMAN metadata
are stored in the recovery catalog indefinitely. Therefore, when you use a recovery catalog, you can access any
historical RMAN metadata.
If you're using only the control file as the RMAN metadata repository, then the information stored there will
eventually be overwritten. The default value for
CONTROL_FILE_RECORD_KEEP_TIME
is 7 days:
SQL> show parameter control_file_record_keep_time
NAME TYPE VALUE
------------------------------------ ----------- ---------
control_file_record_keep_time integer 7
You can set the value to anything from 0 to 365 days. Setting the value to 0 means that the RMAN metadata
information can be overwritten at any time.
The
CONTROL_FILE_RECORD_KEEP_TIME
parameter was more critical in older versions of Oracle, in which it wasn't
easy to repopulate the control file with RMAN information, in the event that metadata were overwritten. Starting with
Oracle 10g, you can use the
CATALOG
command to quickly make the control file aware of RMAN backup files.
If you run daily backups, then I recommend that you leave this parameter at 7 days. However, if you only back up
your database once a month, or if, for some reason, you have a retention policy greater than 7 days, and you're not using
a recovery catalog, then you may want to consider increasing the value. The downside to increasing this parameter is that
if you have a significant amount of RMAN backup activity, this can increase the size of your control file.
