As you know alert log file location determined by the background dump destination it’s specified by backupground_dump_dest parameter

You can find location of alert log with following command.

SQL> show parameter background

NAME TYPE VALUE

——————————— ———– ——————————

background_core_dump string partial

background_dump_dest string D:\ORACLE\PRODUCT\10.2.0\ADMIN\ORCLDATA\BDUMP

Also you can use following command

SQL> select name, value from v$parameter where name=’background_dump_dest’

NAME VALUE

——————– ————————————————————

background_dump_dest D:\ORACLE\PRODUCT\10.2.0\ADMIN\ORCLDATA\BDUMP

For windows platform to find alert log file location run following command on host

Dir /s alert*.log|more

It’ll show you the location & size of alert log file.