Store string form data in attachment

Question

I am passing some data as string from my Visualforce page to apex via apex function, I store that data by in attachment body through apex code. I came to know from response to my previous question that heap size limit is 6MB, so I won't be able to store more data than that.

In my case I have to store one message at a time and then append to same file when next message arrives, apex function will be called on every message, after appending message apex function would return null. So I am not trying to pass more than a few KBs at a time.

Would I be able to utilize all storage limit by following this saving data in a step by step approach? If yes, then limit would be 25 MB?

Also, 25 MB is limit for one attachment or all attachments combined?

Answer 1

First to clear your concepts :

Heap size, in your case, will be considered when you pass more than 6MB of string data from UI to backend in one transaction. (FYI : Each transaction from UI to server will be treated as fresh transaction and your heap limit will get reset with each call)

Also if you want to store one message at a time, then why to fire BackEnd call everytime, just have a list defined in your Javascript and store everything there and at the end fire a sforce Connection to create your attachment on the client side only. By this way you can create an attachment of 25 MB.

25 MB is limit for one attachment or all attachments combined?

25MB is the limit for each attachment.