Can't see any reference to tinyint by System i online resources itjungle.com, I am wondering if it is possible to use it? There was reference to it on IBM and midrange.com but that didn't really help :
IBM say support for tinyint being ported
midrange.com forum post indicates tinyint not part of ANSI standards
'tinyint' is not supported in DB2 for i.
This documentation (IBM i 7.3) on page 96 tells you the available types and you should see that Small Integer is the smallest available numeric type.
You can see also the available numeric types here. Although this link take you to z/OS documentation, the same rules apply.