总是有一些DBA或者工程师安装的数据库不够规范，按照常规讨论找不到告警日志文件。告诉大家一个小方法，不管你怎么不按照套路出牌，我都能找到告警日志。
1、查看参数background_dump_dest
SQL> show parameter dump
NAME TYPE VALUE
background_core_dump string partial
background_dump_dest string /u01/app/diag/rdbms/bdpdb/bdpdb/trace
core_dump_dest string /u01/app/diag/rdbms/bdpdb/bdpdb/cdump
max_dump_file_size string unlimited
shadow_core_dump string partial
user_dump_dest string /u01/app/diag/rdbms/bdpdb/bdpdb/trace
通常告警日志会在background_dump_dest这个参数对应路径下
2、或者使用查找命令
find / -name al*.log
--告警日志的名字是有规律的alert_sid.log，so 你可以find了
3、注意
Note:
The BACKGROUND_DUMP_DEST parameter is deprecated in Oracle Database 12c Release 1 (12.1.0.1).
4、alert_sid.log说明
An alert log in the directory specified by BACKGROUND_DUMP_DEST logs significant database events and messages. Anything that affects the database instance or global database is recorded here. The alert log is a normal text file. Its file name is operating system-dependent. For platforms that support multiple instances, it takes the form alert_sid.log, where sid is the system identifier. This file grows slowly, but without limit, so you might want to delete it periodically. You can delete the file even when the database is running.
