1.查看日志文件位置；

IND_USER@PROD>select inst_id,name,value from v$diag_info;

   INST_ID NAME                 VALUE
---------- -------------------- --------------------------------------------------
         1 Diag Enabled         TRUE
         1 ADR Base             /u01/app/oracle
         1 ADR Home             /u01/app/oracle/diag/rdbms/prod/PROD
         1 Diag Trace           /u01/app/oracle/diag/rdbms/prod/PROD/trace
         1 Diag Alert           /u01/app/oracle/diag/rdbms/prod/PROD/alert
         1 Diag Incident        /u01/app/oracle/diag/rdbms/prod/PROD/incident
         1 Diag Cdump           /u01/app/oracle/diag/rdbms/prod/PROD/cdump
         1 Health Monitor       /u01/app/oracle/diag/rdbms/prod/PROD/hm
         1 Default Trace File   /u01/app/oracle/diag/rdbms/prod/PROD/trace/PROD_or
                                a_4873.trc

         1 Active Problem Count 0
         1 Active Incident Coun 0
           t

 --alert目录为一个xml文件；

 --trace目录中为文本文件；

[oracle@jibo trace]$ pwd
/u01/app/oracle/diag/rdbms/prod/PROD/trace
[oracle@jibo trace]$ ll -atl|grep alert*
-rw-r-----  1 oracle oinstall 99797 Sep 29 14:54 alert_PROD.log
[oracle@jibo trace]$ tail -f alert_PROD.log
Mon Sep 29 14:43:34 2014
Starting background process SMCO
Mon Sep 29 14:43:34 2014
SMCO started with pid=28, OS id=4709
Mon Sep 29 14:54:57 2014
Thread 1 advanced to log sequence 12 (LGWR switch)
  Current log# 3 seq# 12 mem# 0: /u01/app/oracle/oradata/PROD/onlinelog/o1_mf_3_b22567o2_.log
  Current log# 3 seq# 12 mem# 1: /u01/app/oracle/fast_recovery_area/PROD/onlinelog/o1_mf_3_b2256827_.log
Mon Sep 29 14:54:58 2014
Archived Log entry 7 added for thread 1 sequence 11 ID 0x102473b1 dest 1:

--操作系统下查看alert日志，用tail指令；

数据库有什么改动，日志文件就会产生相应的记录

用于查看学习测试最好不过

Oracle动态显示日志