Where is the location of alert log file in oracle?

We often get questions about how to find alert.log file location in oracle, it's easy to find location of alert.log file, below is two different procedures:

1) you can find alert.log location with parameter background_dump_dest.

SQL> select value from v$parameter where name='background_dump_dest';

VALUE
--------------------------------------------------------------------------------
/u0/app/oracle/diag/rdbms/orcl/orcl/trace

-bash-3.2$ cd /u0/app/oracle/diag/rdbms/orcl/orcl/trace
-bash-3.2$ ls
This is alert.log file ----> alert_orcl.log  orcl_j001_25686.trm  orcl_ora_20641.trc

or in SQL *PLUS

SQL> show parameter background_dump_dest

2) To find the location of the diagnostic_dest, you can use the following select

SQL> select value from v$parameter where name='diagnostic_dest';

VALUE
--------------------------------------------------------------------------------
/u0/app/oracle

To know the current ORACLE_SID, you can use following select:

SQL> select instance_name from v$instance;

INSTANCE_NAME
----------------
ORCL

Alert log file consist alert_.log

Therefore my alert log file is : /u0/app/oracle/diag/rdbms/orcl/orcl/trace/alert_orcl.log

good luck.