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