Commented by: Sean Leyne (seanleyne)

You can define your own TINYINT domain which would map to FB SmallInt.

So, there is no real impediment to migration from those other engines/platforms.

Commented by: Roberto Carlos da Silva (robertosistemas)

It is not as simple as this, since the access components would also have to support the TINYINT type.
I'm having trouble migrating a system that is based on the framework: https://www.aspnetboilerplate.com/
Which used data types (enum byte) that is mapped to TINYINT in mysql, sql server and oracle.
In these database managers it works like a charm!
The Solution is not only to create a DOMAIN, but to implement the correct type in the system manager Firebird and also to make the correct implementation in the access components.
I remember that the Firebird .NET driver did a GUID mapping using a tag in the comments field.
I even opened a call regarding this problem in the .NET access drive
Look:
DNET750