for code within SQL server,it's actually pretty easy.

there's a view that contains all references, but you have to run this command in every database:

select *

from sys.sql_expression_dependencies sed

where sed.referenced_server_name is not null

--and sed.referenced_server_name='MyOracle' ??

for programs and otehr stuff:

you have to open the projects/code of the programs, and string search for the string in question...much harder to do, but that's what I've had to do before...searching .vb, .cs ,.dbml,dtsx, files etc