Automatic Start and Stop of Oracle on LINUX

Here's a script to do automatic start and stop of an Oracle instance running on Linux. Note the change of startup and shutdown for 11gR2. I'm sticking with the dbstart and dbshut method until its removed

http://www.oracle-base.com/articles/linux/automating-database-startup-and-shutdown-on-linux.php

Guest Additions on Oracle VirtualBox

To get guest additions working in VirtualBox hosting Oracle Linux 5 update 8 its necessary to download the kernel-uek-devel and dependent packages. Make sure yum is installed and the repository is downloaded then run yum install kernel-uek-devel.

Kernel Panic - Fatal Exception

After installing Oracle Linux 5 Update 8 in VirtualBox everything worked fine until updating packages. After updating packages and rebooting I got the error message below. To fix the problem I had to change a setting in VirtualBox.

The Error:
Kernel Panic - Fatal Exception

The Fix:
In VirtualBox go to Machine -> Settings -> System.
Then Change chipset to ICH9 and check Enable IO APIC checkbox.

Simple HTTP server in Python

To start a very simple HTTP server on a LINUX machine use Python. Change to the directory that contains files to be served then run the command below. Change the port number as required.

python -m SimpleHTTPServer 8080

Specifying comments in SQL to support auditing in Oracle

Adding comments to an SQL statement in Oracle is a good way of providing context to auditing and sql forensic activities directed against an Oracle database audit log. The Oracle Audit trail, and related software like Oracle Audit Vault will capture any comments embedded within an sql statement as part of its normal activities. This, then, provides a way for applications built on Oracle to provide metadata that can assist in analytics performed on the audit record.

As an example, an online shopping cart may audit searches by keyword and may audit individual product pages. At the database level the sql run to generate such pages can be marked with a comment and a textual description of the functionality of the application that uses such a query. This permits application level auditing to be performed in the database, and not require that the auditor is educated in the full set of statements that may be performed by the application. This method of auditing can be done in addition to application level auditing functionality.

Comments are also useful in the enterprise manager to look up statements that are candidates for automated sql tuning.

To add comments to the statement use the following syntax -

SELECT /* [text] */ .....

When the statements require the use of hints ensure the comments do not get in the way of the correct hint definition. Ensure the comments are of the form


{DELETE|INSERT|SELECT|UPDATE} /*+ hint [text] [hint [text]]... */

Finding Day, Month, Year from a date in Oracle SQL using EXTRACT

In Oracle, to get the year, month, day or time from a date its not necessary to parse the date string using the SUBSTR function. Simply use the EXTRACT function and pass in the relevant keyword to get the value as in the following example:

SELECT EXTRACT (year FROM sysdate) "Year" FROM DUAL;

Other keywords that can be passed in are YEAR, MONTH, DAY, HOUR., MINUTE, SECOND. There are also timezone keywords that can be used with timestamps.

The function is useful when used with GROUP BY. For Example:

GROUP BY EXTRACT(month FROM start_date)

Setting the value of a sequence in pl/sql in Oracle

In Oracle there is no direct way to set the value of a sequence once the sequence has been created. To set the sequence value to a specific value it is necessary to either drop and recreate the sequence, not forgetting all of the options specified in the create statement, or to increment the sequence by some positive or negative value to set the current value to the desired value.

To find out the current value of a sequence you can use the currval function on the sequence, but this will only return successfully if the sequence has already been initialized with a call to nextval. Another way to find the value for the sequence is to query the database as follows:

select sequence_name, last_number from user_sequences;

Below is sample pl/sql to set a sequence to the desired value, it defines two variables to store the current sequence and the desired sequence then alters the increment to the difference of those, increments the sequence then resets the sequence increment to the previous value. -


  procedure set_seq is
    l_max_row NUMBER(38,0) := 0;
    l_cur_seq NUMBER(38,0) := 0;
  begin

  --- Now change the sequence
   select max(id_col) into l_max_row from my_tab;
   select my_seq.nextval into l_cur_seq from dual;
   execute immediate 'alter sequence my_seq increment by ' || (l_max_row-l_cur_seq) || ' nocache';
   select my_seq.nextval into l_cur_seq from dual;
   execute immediate 'alter sequence my_seq increment by 1 nocache';
   select my_seq.nextval into l_cur_seq from dual;