DB2 UDB V8 and WebSphere V5 Performance Tuning and Operations Guide

Chapter 4. DB2 UDB V8 and WAS V5 integrated environment 87

Note that, for records with a large number of fields, this type of comparison can

become a rather expensive operation.

So with optimistic update, instead of locking everything, you hope that nobody

else will change the data, or only a few columns are changed. This could be the

case for your application if changes are highly unlikely and always locking the

data would affect scalability. When a conflict does occur, an exception is thrown.

It is important to note that nullable columns are not supported by optimistic

concurrency in WebSphere V5. Nullable columns are excluded from

overqual ...