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?