UPDATE [rem_srv].DB.Schema.TableA
set a.image_id = b.image_id
    ,a.image_name = b.image_name
from [rem_srv].DB.Schema.TableA a, #local_temp b
where a.image_id = b.image_id
   and a.image_name = b.image_name

   
declare @SQL varchar(1000)
SET @SQL = 'UPDATE TableA SET image_name = ''NewName'' WHERE image_id = 42'
EXECUTE (@SQL) AT [rem_srv];   

declare @SQL varchar(1000)
SET @SQL = 'UPDATE TableA SET image_name = ''NewName'' WHERE image_id = 42'
EXECUTE (@SQL) AS USER = 'Oracle user' --user who has rights on TableA
AT [rem_srv]

declare @SQL Nvarchar(1000)
SET @SQL = 'UPDATE TableA SET image_name = ''NewName'' WHERE image_id = 42'
EXECUTE sp_executesql @SQL