3 tier architecture query ? image ?

Question

Hi Well lets say i created a windows forms application with slide show (3 TIER ) . . What i need is when we end user access the app to begin slide show .. The images will roll accordingly .. But were will the image is stored ?? which tier UI OR DATA OR BUSINESS LOGIC TIER ???? .. I hope it will be Data Tier in table i created image DATATYPE .. But what happens when i delete file from where i uploaded will still the file accessable .. i.e under some folder of DB the image gets stored or what happens .. i have many questions regarding this but first let me get clarity n this :) Ty My best reagrds Sunil G

Vulpes · Answer

If you've stored the actual image in the database (as opposed to its path) then it will be stored as a 'binary large object' (or BLOB). This BLOB represents a copy of the image file on disk and if the image is deleted from local storage this won't affect the copy in the database. To keep the two synchronized you'd therefore have to run an UPDATE command to set the BLOB column to NULL. Now as far as the slideshow app is concerned you clearly can't pull all 100000 records from the database inclusive of the image data without running out of memory. A more sensible approach would be to just pull each individual record from the database as and when you need it. The only problem with this approach is that it might be slow with noticeable delays between the user pressing the button and the next image appearing. If it is too slow then one thing you could do would be to extend the database to include the path to the image as well as (or instead of) the image data itself. You can then pull in the image from local storage which should be quicker.

Vulpes · Answer

Images take up a lot of memory. Consequently in a typical slide show application the images are loaded in from disk as the user cycles through them. This means that the application only needs to store an array of filepaths - in fact it might not even need to do that if the images are all in the same folder and are numbered consecutively. You could store the array in either the UI or data tiers - it doesn't really matter. If you might delete some images then you'd probably want to re-load the array each time the slide show is being used rather than just once when the application starts.

SUNIL GUTTA · Answer

what happens lets say there is a table with empidnamedesignationimage .. well from windows forms i entered the details and loaded image and finally stored in sqlserver .. so when ever i create a slide show i will get contacts with respect to there name everything supposed to get . . . Say it a huge collection i.e around 1lakh records inc images .. Initially i load images from my local system to db Right via windows form as medium .. Later created a UI for accessing data from DB where records inc respective images are present .. .. UI : It have to be lite weight right . .. BL : I written logic at business logic level .. .. DB : All records are present right .. But my unknown question still is IMAGE FILE I LOADED INITIALLY FROM LOCAL SYSTEM LATER STORED INTO DB  WHEN ACCESSED FROM OTHER UI CREATED .. were will the images gets stored ? in DB means were ? in table or table referencing the image ?? another copy will gets stored aa after storing into DB ... When i delete image file from local system will records gets affected aaa I am confused and also confused to explain what i need