Enabling archive redo log mode is a prerequisite for making online backups. 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
- Location specified via the 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,
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:
I also prefer to use this format for the default archivelog file name:
Tip 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.