Database Reference
In-Depth Information
4. Setting the Archive Redo Log Destination and File Format
Enabling archive redo log mode is a prerequisite for making online backups (see Chapter 2 for a full discussion of
architectural decisions regarding the archive redo log destination and format and how to enable/disable
archivelog mode).
When archivelog mode is enabled, Oracle writes the archive redo logs to one or more of the following locations
(you can configure archive redo logs to be written to the FRA as well as to several other locations that you manually set
via initialization parameters):
•
Default location
•
FRA
LOG_ARCHIVE_DEST_N
initialization parameter(s)
If you don't use an FRA, and if you don't explicitly set the archive redo log destination via a
LOG_ARCHIVE_DEST_N
initialization parameter, then by default the archive redo logs are written to an OS-dependent location. On many
Linux/Unix boxes the default location is the
ORACLE_HOME/dbs
directory. The default file name format for archive redo
logs is
%t_%s_%r.dbf
.
If you enable an FRA (and don't set
LOG_ARCHIVE_DEST_N
), then, by default, the archive redo logs are written to a
directory in the FRA. The default file name format of the of archive redo log files created in the FRA is an OMF format.
The files are stored in a subdirectory given the same name as the database's unique name; for example,
•
Location specified via the
/<fra>/<dbuname>/archivelog/<YYYY_MM_DD>/o1_mf_1_1078_68dx5dyj_.arc
Oracle recommends using an FRA. I prefer not to use an FRA because I don't like to be surprised with a hung
database when there are issues with the FRA's filling up and not being purged of old files quickly enough. Instead, I
use the
LOG_ARCHIVE_DEST_N
parameter to set the location of the archive redo log files. Here is an example:
log_archive_dest_1='LOCATION=/oraarch1/CHNPRD'
I also prefer to use this format for the default archivelog file name:
log_archive_format='%t_%s_%r.arc'
■
Sometimes, DBas use
.dbf
as an extension for both data files and archive redo log files. i prefer to use
.arc
for
the archive redo log files. the
.arc
extension avoids the potentially confusing task of identifying a file as an archive
redo log file or a live database data file.
Tip
5. Configuring the RMAN Backup Location and File Format
When you run a
BACKUP
command for disk-based backups, RMAN creates backup pieces in one of the following locations:
•
Default location
•
FRA
BACKUP...FORMAT
command
•
Location specified via the
CONFIGURE CHANNEL...FORMAT
command
•
Location specified via the
Of these choices, I lean toward the last of them; I prefer specifying a target location via a backup channel.
