From the menu you have a variety of choices of which matches to replace:
n The current search match
n All matches in the current entity
n All matches in the current module
n All matches in the current application
n All matches
There is also a Repl. Current button beneath the Find button to replace just the current match.
Global Search & Replace performs replacements immediately and directly to the matched entities. If you have any editor windows open they will not be automatically refreshed with the new entity source code. Global Search & Replace can also make widespread changes to your project, and you should perform replacements with care. Because of this Global Search & Replace will warn you prior to making a change: