How To Check Alert Log File in Oracle 11g

Each database has an alert log file, which contains a chronological(sequential order in which they occurred) log of database messages and errors. Oracle will automatically create a new alert log file whenever the old one is deleted.

Alert Log Location in Oracle 11g

The alert log includes the following errors and log messages:


  • All internal errors (ORA-600), block corruption errors (ORA-1578), and deadlock errors (ORA-60)
  • Administrative operations such as DDL statements and the SQL*Plus commands STARTUP, SHUTDOWN, ARCHIVE LOG, and RECOVER
  • Several messages and errors relating to the functions of shared server and dispatcher processes
  • Errors during the automatic refresh of a materialized view

How to Find the Location of alert log file in Oracle 11g


SQL> select name from v$database;

NAME
---------
TEST11


alert.log file is written to the directory specified by the background_dump_dest parameter. To view alert log, first you need to find it's location using show parameter command.


SQL> show parameter background_dump_dest

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
background_dump_dest                 string      /u01/orahow/diag/rdbms/test11/TEST11/trace


You can also get the same result using this sql:


SQL> show parameter background

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
background_core_dump                 string      partial
background_dump_dest                 string      /u01/orahow/diag/rdbms/test11/TEST11/trace

 Copy the above value to find the exact name and location of alert log using ls command:
                                              
[oracle@orahow ~]$ ls -ltr /u01/orahow/diag/rdbms/test11/TEST11/trace/al*
-rw-r----- 1 oracle dba 1901154 Nov 24 04:00 //u01/orahow/diag/rdbms/test11/TEST11/trace/alert_TEST11.log

To view alert log you can use tail command with options and filename.

[oracle@orahow ~]$ tail -20f /u01/orahow/diag/rdbms/test11/TEST11/trace/ alert_TEST11.log
In the following output you will see the last 20 lines of the alert log, but if you want to see more number of lines (ex: 100 line) you can use 100f like that.
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How to Make a File Write Protected in Linux

In Linux there is an additional file attribute which prevent files and folders from being deleted accidentally. Flag which make a file write/delete protected even from root is called immutable flag. Linux administrator must set this flag for various configuration files on the production servers so that no one could delete/temper with these files.


Prevent file from being deleted


When you want to delete file/folder having immutable flag set, you will encounter with an error:
rm: cannot remove 'file-name': Operation not permitted.

Making file write protected in Linux

To set this flag we use plus (+) sign with chattr command and to unset this flag we use minus (-) sign.


Syntax:

To set this flag on files you can use the following command:
chattr +i filename

To unset or remove the attribute you can use the following command:
 chattr -i filename 


To set this flag on directories only you need to specify the directory name:

 chattr +i directory name 

chattr -i directory name 


How to search files having immutable flag set?
To accomplish this we use lsattr command pipe with the grep command.

lsattr -R | grep +i

Example:

Creating file having name san.txt and setting flag on it.
[oracle@orahow ~]$ vi san.txt

Initially check the file permission:
[oracle@orahow ~]$ ls -l san.txt
-rw-r--r-- 1 oracle dba 19 Nov 18 05:56 san.txt

 [oracle@orahow ~]$ chattr +i san.txt

chattr: Operation not permitted while setting flags on san.txt


To set this flag you need to login as a root user:

[root@orahow oracle]# chattr +i san.txt

[root@orahow oracle]# lsattr san.txt
----i-------- san.txt 


Now try to delete the file having immutable flag set:
[root@orahow oracle]# rm san.txt

rm: remove write-protected regular file `san.txt'? y

rm: cannot remove `san.txt': Operation not permitted

To remove this file you need to unset this flag:

[root@orahow oracle]# chattr -i san.txt

[root@orahow oracle]# lsattr san.txt

------------- san.txt

[root@orahow oracle]# rm san.txt
rm: remove regular file `san.txt'? y
[root@orahow oracle]# cat san.txt
cat: san.txt: No such file or directory

Making a directory write protected in Linux:

[root@orahow oracle]# mkdir san
[root@orahow oracle]# ls -ldr san

drwxr-xr-x 2 root root 4096 Nov 18 07:36 san

[root@orahow oracle]# chattr +i san
Now if you try to remove the directory it will throw a message: operation not permitted. Before deleting this folder you need to unset this flag.

[root@orahow oracle]# rmdir san
rmdir: san: Operation not permitted

[root@orahow oracle]# chattr -i san

[root@orahow oracle]# rmdir san

[root@orahow oracle]# ls -ldr san

ls: san: No such file or directory




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