ORACLE 11g case insensitive by default

You could just set the NLS_SORT, NLS_COMP parameters mentioned in the article as the values in the the Oracle init file using the alter system set <parameter> = <value>; clause.

Info on using the alter system commands can be found here.

Here is a good link on the correct usage of the NLS_* parameters. Note that some settings of of the NLS_SORT parameter can/could cause performance issues, namely when it is not set to BINARY. The Oracle docs state:

Setting NLS_SORT to anything other than BINARY causes a sort to use a full table scan, regardless of the path chosen by the optimizer. BINARY is the exception because indexes are built according to a binary order of keys. Thus the optimizer can use an index to satisfy the ORDER BY clause when NLS_SORT is set to BINARY. If NLS_SORT is set to any linguistic sort, the optimizer must include a full table scan and a full sort in the execution plan.

Sure you can!

Get your friendly DBA to set these parameters:

ALTER SYSTEM SET NLS_COMP=LINGUISTIC SCOPE=SPFILE; ALTER SYSTEM SET NLS_SORT=BINARY_AI SCOPE=SPFILE; 

This is taken from my short article on How to make Oracle Case Insensitive

I tried using a logon trigger to issue these commands to get case-insensitive queries:

execute immediate 'alter session set NLS_SORT=BINARY_CI';execute immediate 'alter session set NLS_COMP=LINGUISTIC';

And while that did give me CI, it also gave me unbelievably bad performance issues. We have one table in particular that, without those settings, inserts take 2 milliseconds. With those settings in place, inserts took 3 seconds. I have confirmed this by creating and dropping the trigger multiple times.

I don't know if doing it at the system level, as opposed to the session level with a trigger, makes a difference or not.