What is the difference between SIT and EIT

I have heard of this question so often (including today), that I have decided it is worth investing the time to put up a blog on this. Before I go forward, it is worth pointing out that SITs pre-date EITs. From what I recall, EITs were not introduced until 11i.

So, here is the difference between Special Information Types (SIT) and Extra Information Types (EIT):

Property	SITs (Special Information Types)	EITs (Extra Information Types)
Screen usage	SIT's are primarily attached to people. (They can also be used with Jobs and Positions)	EIT's can be attached to following screens: - People e.g. - My Passport Information - Assignment e.g. - Daily Work Schedule - Location e.g. - US Government Reporting - Organization (via a classification) - Job - Position - Element Types, etc.
Date Information	The SIT form has NATIVE Start Date and End Date fields	EIT forms do not have native Start Date and End Date fields Typically, we would 'reserve' two EIT segments to store Start Date and End Date across any EIT. E.g. say ATTRIBUTE29 and ATTRIBUTE30
Security	SITs can be restricted so that they can be viewed only by responsibilities having specific Menu. For example, to control access to Compensation related SITs, we build two separate Menus - SALARY Menu and NO SAL Menu; then select the appropriate menu to restrict access to SITs	EITs can be restricted to be viewed only by specific Responsibility. For example, if you want to store highly sensitive data that should be visible by only one or two top level responsibilities, this is easily accomplished using an EIT (To achieve same result using an SIT, a separate Menu needs to be built each time, resulting in a large number of Menus, which can be increase complexity and maintenance)
Folders	SIT's have a folder that you can query to match certain criteria. Nav: View> Lists> People by Special Information	EIT's do not have a pre-defined folder
Enabling the structure	SIT has to be enabled individually for each Business Group	Once configured, an EIT is available across all business groups. To access the EIT, it just needs to be attached to a Responsibility.
Field Structure	For each SIT, you can define up to 30 fully validated segments of information	For each EIT, you can have up to 30 fully validated segments of information. In addition, you can define 20 additional DFF segments on the EIT
Structure Type	SIT's are a type of Key Flexfields (KFFs)	EIT's are a type of Descriptive Flexfield (DFFs)
Data Storage	When you create new segment combinations, the system will first check to see whether that combination already exists in the table before creating a row. If the combination does exist, the system only retrieves the ID of the row it found. The system therefore has to scan through the whole SIT combinations table. If this is very large, performance could be an issue.	When you create new segment combinations, the row is just inserted into the appropriate table (without checking whether the combination already exists). There is no full scan of the underlying table and so performance isn't affected by the size of the table. Thus, EIT's have advantages in large scale or global implementations
Key Advantages	Can be restricted by Menus. For example, if there is a Salary related SIT, we can ensure that responsibilities having NO SALARY menus cannot access this SIT (There is no easy way to accomplish this for EITs)	1. Can be accessed on multiple screens like assignment, people, etc. 2. EITs have the flexibility to be defined as Single Row (i.e. each employee can have only one row of data) or Multi-Row (Such restriction is not possible using SITs) 3. Can be restricted by legislation code. For example - US Union EIT is restricted such that it can be attached only to Business Groups using US Legislation
Disadvantages	Every unique combination of fields is stored as separate "Definition". When saving an SIT record, the Application first checks whether the combination already exists in the table. Therefore, if number of records is very large, SITs require more processing time.	Every time a new Responsibility is created, EITs have to be separately attached to the Responsibility

If there are other differences you want to know about, or you want to contribute on, please leave a comment and I will make sure I include that in the blog.