The alert log records database shutdown and startup times, certain configuration changes e.g. datafile resizing and lots more besides. Up to and including Oracle version 10, you can find the alert log in the directory specified by the background_dump_dest initialization parameter. Its default value is $ORACLE_HOME/rdbms/log:
1 select value, isdefault, issys_modifiable
2 from v$parameter
3* where name = 'background_dump_dest'
VALUE ISDEFAULT ISSYS_MOD
------------ --------- ---------
?/rdbms/log TRUE IMMEDIATE
According to the query above, you can modify this parameter and the change should take place immediately i.e. without having to reconnect to the database. I tried this as follows:
1 alter system set background_dump_dest =
It did not work i.e. entries continued to appear in the original alert log. This is a bug reported on Metalink as 3412765 and 6124649. There are no plans to fix it so, if you want to use a non-standard location for your alert log, you must include a background_dump_dest line in your parameter file before opening the database.
Oracle deprecated the background_dump_dest parameter in Oracle 11 when the diagnostic_dest parameter was introduced.