Where is my database alert log file ??

Oracle 11g introduce new error and alerting system within Automatic Diagnostic Repository, the alert log file is now by default store in ADR trace directory.

The Diag Trace is the path where the text base alert log file is store.
The Diag Alert is the path where the xml version of alert log file is store. This version can be read with Enterprise Manager and Oracle ADRCI utility.

Issue following command to show the ADR path architecture.

SELECT name, value FROM v$diag_info;

When you list the path you should able to locate your alert log file. Note the text base alert log file naming is alert_[SID].log

ls -l /u01/app/oracle/diag/rdbms/edba01/edba01/trace/alert_edba01.log

ls -l /u01/app/oracle/diag/rdbms/edba01/edba01/alert/log.xml

The parameter file that tell Oracle where should the alert log file store is background_dump_dest, you can also query the parameter file by using following command

SHOW PARAMETER background_dump_dest

With Oracle 11g onwards I do not have to set the background_dump_dest parameter anymore as it going to follow the ADR architecture.