Value Sets vs Lookups

I was using independent value sets for every need for value lists. A few days ago i learnt that using lookups for value lists are more cost effective because it is using one table to store data though value sets are using two tables.
Then a question emerged: when to use value sets? When we need dependent values, when we need to use selects from tables, when we need to list long values etc. Also there is advantage of validation for Value Sets; with special and pair validation types value set validation can be changed depending on the transaction type: insert-update, edit, query etc.

Query on Oracle Forms

Searching in the Oracle EBS forms was simple and straightforward for me until last week.
I have learned two ways to increase search capabilities in the forms:
1- Press f11 to turn on the query mode, help>diagnostics>examine then you
can select any field which you know and doesnt seem on the form screen (such as id) then press ctrl+f11...
2- In query mode you can query by conditions like "<,>, is (not) null". Firstly type "#", secondly your condition then execute the query with ctrl+f11 ...

Audit table

Last week i have learned that Oracle gives you the chance of tracking changes of tables you want. Whenever a change
occurs for the columns you selected, it creates a record. It seems to be a very
useful feature. It is kind of technical staff though steps to implement are easy and
functional:
AuditTrail:Activate profile should be set to 'Yes'
system administrator>security>install enable audit for your oracle username
system administrator>security>groups create an audit group, define the tables in the group. (Custom tables should be registered to be listed here)
system administrator>security>tables columns, desired to trail, should be selected.
AuditTrail Update Tables concurrent should be run.
After the concurrent a new table should have been created, which has "_a" after the original table name.

Outer join use

Normally SQL does not allow to use a table with more than 1 outer join (+), how to solve the problem is a mystery for me. Previously i have read that ANSI code could be used for this though i haven' t use it yet. Today i have seen a discoverer report which uses some selects as tables to avoid outer joins and unions. Writer of the report says it also improves the performance, i will try it when the time arrives...